"■'■■■ ■ . . ■ • • •' ■.. ' ' ■ :-.■■'••; '■■' . Ji^Wi Watchfulness Hand-Picking Insecticides Ridding the Garden of Common A. E. Micheibacher John E.Swift C.S. Davis Dennis H. Hail Robert D.Raabe CALIFORNIA AGRICULTURAL Experiment Station The Home Gardener grows flowers for fun and vegetables for the family. But each year both fun and family suffer because of the activities of numerous insect pests. INSECTS and RELATED PESTS invade the garden from planting of the seed to har- vesting of the crop. Many of them can be controlled quite easily. But to attempt any control the gardener must • Be able to identify the pests # Hand-pick and destroy all pests found 9 Maintain clean cultural practices <§; Have a basic knowledge of insecticides and what they will do This circular is planned to help the home gardener in all four phases of his pest-control problem. PLANT DISEASES also invade the garden but many of them are not so easily con- trolled as are the insects. In fact, for some diseases highly satisfactory control measures are not yet known. The home gardener must control these largely by prevention and not by remedy. This circular presents a few suggestions for the control of the most common diseases, and encourages the gardener to take a very practical view of the disease problem. JUNE, 1959' The Authors: A. E. Michelbacher is Professor of Entomology and Entomologist in the Experiment Station, Berkeley. John E. Swift is Extension Entomologist, Berkeley. C. S. Davis is Extension Entomologist, Berkeley Dennis H. Hall is Extension Plant Pathologist, Davis. Robert D. Raabe is Assistant Professor of Plant Pathology and Assistant Plant Pathologist in the Experiment Station, Berkeley. Danger All insecticides are poisonous and must be used with great caution. Some of the most effective, such as parathion, Systox, or TEPP are so dangerous that they cannot be recommended for use in home gardens. Some that can be used may be less hazard- ous than others, but extreme care must be exercised with all materials used in pest control. Here are precautions that must always be observed: Keep insecticides in their original properly labeled containers. Avoid pouring chemicals into a pop bottle or a similar vessel, and never store chemicals in such a container. Keep all insecticides and chemicals out of the reach of children. Store preferably under lock and key, but at least place on high shelves where children or pets cannot reach them. A dark storage place is preferred, because any material which oxidizes will do so more readily in sunlight. Wash out empty containers and properly dispose of them through burying or placing them in garbage can. Avoid contamination of skin or clothing, particularly with undiluted spray materials. After using insecticides, thoroughly wash the hands and face with soap and water; a change of clothing is advisable. Avoid inhaling insecticides when handling, mixing, and applying them. Wash any piece of equipment thoroughly after using it. This in- cludes mixing spoons and measures. Wash out sprayers with plenty of water and place them on end to drain. Read directions on container and note all the precautions given before using the chemical. Change immediately if spray is spilled on clothing, and wash or bathe thoroughly. There are 2 kinds of insect pests These two general groups are divided by their method of feeding: chewing or sucking. CHEWING PESTS Chewing pests are usually larger than pests with sucking mouth parts. They eat very noticeable holes in the parts of the plant on which they feed, and in some cases bore into the parts attacked. This characteristic injury suggests the best method of control. For the chew- ing pests, use stomach poisons or some of the newer insecticides that exhibit both stomach and contact action. Chewing insects commonly found in the home garden and covered in this cir- cular are: ants, Brachyrhinus weevils, bristly rose slug, bulb fly, cabbage worms, corn earworm, cricket, cucumber beetles, cutworms or armyworms, Euro- pean earwig, flea beetles, grasshoppers, hornworms, leaf miners, leaf tiers and leaf rollers, pea weevil, root maggots, sod webworms, or lawn moths, tomato pin- worm, vegetable weevil, and wireworms. Although they are not insects, the fol- lowing pests have chewing habits and are treated in the same way as insects: garden centipede or garden symphylid. land planarians, snails and slugs, sow- bugs, pillbugs, and millipedes. SUCKING PESTS Sucking pests insert their mouth parts into the plant tissue and suck the juice. They may produce stunted or deformed areas. The plant, if heavily infested, gradually dries up. Some sucking insects inject toxic materials into the plant and others excrete quantities of honeydew upon which the sooty mold fungus grows. For the sucking insects use contact insecticides and fumigants. Sucking insects causing the home gar- dener the most trouble, discussed in this circular, are: aphids, harlequin cabbage bug, leafhoppers, Lygus bugs, stinkbug. mealybugs (aerial and soil), scales (armored and unarmored) squash bug, thrips, tomato psyllid, and whiteflies. Re- lated sucking pests are spider mites or red spiders, the tomato Russet mite, and root knot nematode. Watch for pests . . . . . . This is the first step in the successful control of garden pests. The gardener simply cannot plant flowers or vegetables and go away and leave them. A host of pests is waiting for him to turn his back. The watchful eye of the gardener — frequently scanning the ground around newly set plants, or checking the under- side of leaves, or closely examining the budding fruits and flowers — is the con- trolling factor for which there is no sub- stitute. Most destructive pests are small and unless they are carefully looked for may escape detection until they have caused serious damage. Some insects feed only at night. These are sometimes re- vealed by examining the plants at night with a flashlight. Hand-pick the pests . . . . . . and destroy all found. This is an old- fashioned method of controlling insects. Nevertheless, it still is effective in home gardens against such pests as squash bug. hornworms, leaf-feeding caterpillars, har- lequin cabbage bug. snails, and slugs. Maintain a clean culture . . . . . . This step in pest control is frequently overlooked. Remnants of plants should be destroyed as soon as the harvest is com- pleted. Weeds must not remain about a garden since they serve as breeding places for many insects and mites. Burn or spade under rubbish piles and plant refuse. Use insecticides . . . . . . Many times insecticides are the only dependable means of holding the insects under control. Insecticides can be roughly divided into three groups: stomach poisons, con- tact insecticides, and fumigants. With the advent of many of the new insecti- cides this classification has lost much of its meaning because a number of the newer organic materials act as both stomach and contact poisons; in addi- tion, some exert a fumigant action. Insec- ticides are continually being improved, and recommendations for their use are changing. For this reason it is important to read carefully the directions given on each new container you purchase, and to follow them exactly. [5] ■ How to use STOMACH POISONS Cryolite (sodium fluoaluminate ) , cal- cium arsenate, and lead arsenate are strictly stomach poisons. Each of these has peculiarities which make it more, or less, suitable for the job to be done. Cryolite (sodium fluoaluminate) is much less toxic to human beings and other warm-blooded animals than either calcium or lead arsenate, and is there- fore recommended in preference to the others for home vegetable gardens. Calcium arsenate is extremely effec- tive as a stomach poison for garden pests — but unfortunately also for humans and animals. The drift from this insecti- cide, when used as a dust, has poisoned animals that have eaten the contaminated foliage and bees that have visited the flowers. Also, it is injurious to the foliage of certain plants. Lead arsenate should never be ap- plied to any vegetable crop or vegetation if the foliage is intended for either human or animal consumption. DUST VEGETABLES For vegetable gardens these stomach poisons are probably most easily and efficiently used as dusts. The following rules will help you do a good job: 1 . Regulate dusting apparatus to pro- vide a light and thorough coverage. 2. Emphasize light coverage. Never overapply or pile the dust into the center of the plants. Where the ground is well covered with vegetation and the rows are 18 inches apart, use about V2 ounce of dust to each 20 feet of row. 3. Apply dusts in early morning or evening when there is little or no wind. Drift of insecticides to other plants must be reduced to a minimum. Never allow poison dusts to drift to adjoining property. SPRAY CUT FLOWERS AND ORNAMENTALS Because flowering plants and orna- mentals present only a slight problem of poison residue, they may be successfully sprayed. With this method of application danger from drift is reduced. Lead arsenate is probably the most effective of the strictly stomach poisons and is well adapted for use as a spray. The standard spray mixture of this in- secticide is V2 ounce of lead arsenate to 1 gallon of water. The following suggestions apply to the use of any spray material. 1 . Prepare a fresh batch of spray solu- tion each time you spray the garden. Put it in a clean applicator. Follow the in- structions on the container. 2. Use a "sticker" or wetting agent, as recommended by the manufacturer: or use a paste-type oil emulsion. 3. Wet thoroughly all parts of the plant when applying the spray. 4. Allow spray to dry before watering plants. 5. Apply spray in early morning or late evening; this is the best time to spray STOMACH POISONS FOR CHEWING PESTS T6] because of minimum wind. However, do not apply sprays to plants heavily wet with dew. CONTACT INSECTICIDES The contact insecticides include such old standbys as nicotine and lime- sulfur. Pyrethrum and rotenone have be- come well established over a number of years. Refined mineral oils are valuable in killing insects, particularly when com- bined with one of the organic insecti- cides. In addition to these there are a number of new organic insecticides — organic phosphates, organic thiocyanates, and chlorinated hydrocarbons. Most of these have complicated chemical names which mean a great deal to the men in the laboratory who discover and make them. Their common names, however, are more familiar to the home gardener. These organics, using their more com- mon designations, include: Malathion, DDT, DDD, methoxy- chlor, toxaphene, lindane (gamma isomer of benzene hexachloride), chlordane, dieldrin, aldrin, hepta- chlor, Aramite, and Kelthane. All of these compounds kill by contact ; in addition, some of them may act as stomach poisons. The above-listed insecticides are sold as commercial preparations either as liquid concentrates or wettable powders to use for spraying or dusting, or as pel- lets, or in a granular form to be applied by a duster or broadcast by hand. The concentrated spray products should be diluted with water and applied with ordinary pressure sprayers. Aerosol bombs designed for garden spraying to wet the treated surface are also available and can be effectively used to control certain garden pests, especially many of those infesting house plants. SPECIFIC USES Most insecticides or groups of insec- ticides have specific uses or are especially effective on certain pests or groups of pests. DDT, DDD, methoxychlor and lin- dane are most effective on such chewing pests as worms or caterpillars, beetles, weevils, and against some sucking pests such as thrips, leafhoppers, some aphids, and Lygus bugs. Because of the relatively long residual effect of these materials, they should not be applied to vegetables within three weeks of harvest. On certain vegetables that cannot be washed or wiped, applications should not be made after the fruiting bodies begin to form. These insecticides can be applied to flow- ering plants at any time. Chlordane, dieldrin, aldrin, and heptachlor are effective against ants, grasshoppers, earwigs, root maggots, some weevils, wireworms, bulb fly, some leaf miners, lawn moths, and certain other pests. These materials should not be applied to the edible portions of vege- tables unless their residue can be removed by washing, wiping, or stripping. They should not be used on leafy vegetables later than the seedling stage. Malathion is effective against aphids, spider mites, scale insects, mealybugs, millipedes, and some of the other pests previously mentioned. Its relatively short residual action and low toxicity make its use possible to within seven days of har- vest. Malathion can be safely applied to vegetables, flowering plants, and orna- mentals at any stage of growth. This ma- CONTACT INSECTICIDES FOR SUCKING PESTS [7] terial is frequently used in combination with other pesticides. Aramite and Kelthane are known as acaricides or miticides. These prod- ucts are effective only on spider mites. Aramite should not be applied to the edible portion of any vegetable or fruit crop. Both products can be used on most ornamentals and flowering crops. Fre- quently they are combined with other in- secticides in order to control several pests with one application. Nicotine sulfate (Blackleaf 40), one of the most common spray materials, is particularly effective against aphids and thrips. Nicotine is frequently used in combination with other insecticides and fungicides. Pyrethrum and rotenone, when used as sprays, are effective against aphids, leafhoppers, thrips, and many other soft-bodied insects. Pyrethrum dusts should contain 0.10 to 0.25 per cent pyrethrins and 2 per cent organic thiocyanate applied at temperatures below 65° F give excellent control of leafhoppers, thrips, and cu- cumber beetles. Rotenone dusts containing at least 0.5 per cent rotenone are effective against pea weevil, pea aphid, and small cabbage worms. The highly refined mineral oil emul- sions are available alone or in combi- nation with nicotine, pyrethrum, rote- none, or with some of the new organic insecticides. They are highly effective in killing a wide range of insects including certain aphids, scales, mealybugs, leaf- hoppers, thrips, beetles, and caterpillars. Nicotine, pyrethrum, rotenone, or- ganic thiocyanates, mineral oils, and malathion are relatively nontoxic to man after they have been applied and then allowed to "weather" for at least seven days. They can be applied to most plants at any stage of growth. COMBINATION INSECTICIDES The home gardener is most interested in controlling a wide range of insects with few applications. Many chemical companies are now packaging combina- tions of insecticides for the control of numerous pests of both the sucking and the chewing types. Some of the combinations also include fungicides to aid in the control of plant diseases. Examples of these combined products are: rotenone, pyrethrum, and petroleum oil; petroleum oil, nicotine, and DDT. Other combinations may con- tain lindane, Malathion, DDT, or meth- oxychlor; and fungicides such as captan, zineb, ferbam, and ziram; or chlordane and toxaphene; or dieldrin and lindane; or dichloroethyl ether and lindane. Numerous combinations are available, and the gardener should compare them, carefully reading labels and directions before buying. We cannot overemphasize the need to follow directions on the package. Most of the new products are continually un- dergoing change as more about them is learned through usage. Recommenda- tions made by the manufacturer may change for the same product over a period of a few months. Overapplication of insecticides should be avoided. There is evidence that some insecticides such as DDT and dieldrin may accumulate in the soil, through pro- longed use, to a level where they may prove injurious to certain varieties of plants that may be grown at a later date. Another question is the danger of destroying beneficial insects, particularly bees, ladybird beetles, and other common predators and parasites. It is also possible that while these in- secticides will kill certain insect pests, they may actually encourage an increase in other pests. In part this is brought about by the destruction of natural enemies. [8] Also, some insecticides induce in- creases in pest populations through phys- ical or physiological processes. The exact nature of these stimulations is not as yet fully understood. For example there is danger of serious increases in the population of red spiders where such materials as DDT, DDD, dieldrin, heptachlor, and aldrin are used. To combat this problem, many manu- facturers are now adding sulfur to the product, or a material such as Aramite or Kelthane to destroy the developing spider mite population. The gardener can help to eliminate the adverse effects of these insecticides by using just enough and no more than is necessary for adequate control. THIS IS WHY DIRECTIONS ON THE PACK- AGE MUST BE FOLLOWED. FUMIGANTS Fumigants are not widely used for the control of insect pests in the home gar- den. They are found practical only for the control of certain underground pests. Dichloroethyl ether is used for the control of sod webworms, ground mealy- bugs, and cabbage maggots. Ethylene dibromide is very effective for controlling wireworms, root weevils, and the root-knot nematode. Both of these fumigants are for sale in small packages, and the directions for their use are given on the containers. EQUIPMENT Sprayers. A satisfactory sprayer breaks the liquid into a fine mist. Its nozzle can be held at various angles in order to wet the underside of foliage. In the photo below — at left is a good type sprayer for the fairly large garden ; it is worn on the back of the operator and the up and down motion of the handle cre- ates pressure and works the agitator. At suitable for large gardens. Pressure is built up by pumping but there is no agi- tator so material must be well mixed before filling the sprayer. In the center is a small atomizing type, good for house plants and window boxes but too small for general use. At the top of page 10 appears a hose attachment sprayer which is good for gen- the right is a pressure-type sprayer also eral outside spraying. Liquid spray con- 3H}B3595a8HM6jittiC>&yffi*v L> B // m wBl'-.; ^l?WJB@8mS^M^.^^y' centrate is put in the jar, metered out and diluted for proper rate of application by water pressure from the hose. Dusters. A good duster regulates the flow of dust to avoid blobbing It is un- necessary to buy the most expensive duster to get good performance. Photo below shows: Top, small, inexpensive dusters that are very efficient for use in a small garden. Right, bellows type worn on the back and suitable for very large gardens where plants are continuous. Left, rotary type carried in front of the operator, also good for large gardens and continous plantings. [10] Most of the stomach poisons, and many of the new insecticides, are extremely in- jurious, or even fatal, if eaten by human beings, livestock, cats, dogs, chickens, and bees. They must be used with the greatest possible caution. Cryolite, calcium arsenate, DDT, DDD, and lindane leave poison residues which remain on the plant long after ap- plication. If any of these chemicals has been applied to edible portions of plants (for instance, tomatoes), carefully wipe, wash, or peel before serving. On cauliflower, cabbage, lettuce, and similar vegetables, do not use any of these materials after the heads have begun to form. On leafy vegetables that do not head, these materials should not be ap- plied after the plants are up and estab- lished. On beans, peas, squash, cucumbers, and similar vegetables do not apply after the fruit is set. Lindane (gamma isomer of benzene hexachloride) is an insecticide relatively free of odor but one that must be used with considerable caution because it may impart an off flavor to certain vegetables. In using poison bait, avoid scattering the material on the plants, and keep con- tainers out of reach of children and pets. DDT and most other of the new or- ganic compounds are poisonous to fish and other cold-blooded animals. Avoid spraying into lily pools, fish ponds, and streams. Where insecticides might drip into pools, cover the pools before spray- ing. In handling, mixing, and applying poisonous insecticides, take special care not to inhale the spray, or let it drip on your clothes, hands, or arms. When the job is finished, thoroughly wash the hands as well as other parts of the body which may have been exposed. If cloth- ing is contaminated by an insecticide, remove clothing, bathe, and do not wear these garments again until they have been thoroughly laundered. Have a special storage place for cans and packages of materials so that they can be kept out of reach of children and pets. Be certain that all containers are labeled. Keep the storage place locked. A dark storage place is preferred, be- cause any material which oxidizes will do so much more readily in sunlight. After using any piece of equipment, wash it thoroughly. Wash mixing spoons and containers. Invert sprayer to drain. [ii CONTENTS Chewing Pests Ants 13 Brachyrhinus weevils 13 Bristly rose slug 14 Bulb fly 15 Cabbage worm 16 Corn earworm 16 Cricket 17 Cucumber beetles 17 Cutworms or armyworms 18 European earwig 19 Flea beetles 19 Garden centipede or garden symphylid . 20 Grasshoppers 20 Hepialid moth 21 Hornworms 21 Land planarians 21 Leaf miners 22 Leaf tiers and leaf rollers 22 Millipedes 23 Pea weevil 23 Root maggots 24 Snails and slugs 24 Sod worms or lawn moths 25 Sowbugs and pillbugs 26 Tomato pinworm 27 Vegetable weevil 27 Wireworms 28 Sucking Pests Aphids 28 Harlequin cabbage bug 29 Leafhoppers 29 Mealybugs (aerial) 30 Mealybugs (soil) 31 Scales (armored) 31 Scales (unarmored) 32 Spider mites or red spiders 33 Squash bug 34 Thrips 34 Tomato psyllid 35 Tomato russet mite 35 Whiteflies 36 Root-knot nematode 37 Diseases Soil-borne diseases 38 Damping-off diseases 38 Water mold root rot 39 Armillaria root rot 39 Verticillium wilt 40 Salt damage 41 Mineral deficiency diseases 41 Stem, foliage, and flower diseases (powdery mildew) 42 Sunburn 43 Rust diseases 43 Twig dieback of rose 44 Anthracnose of sycamore 44 Scorch of Modesto ash 44 Fire blight 44 Peach leaf curl 45 Iris leaf spot 46 Virus diseases 46 [12] Chewing Pests The Pests ANTS Ants are social insects, living in colonies, that are found nearly every- where. Depending upon the species, they build their nests in open ground, under stones or wood, in wood or decaying trees, or in any other location that offers protection. Ants are generally wingless except at mating time. At that period swarms of recently emerged winged males and fe- males can be seen. Soon after mating the males die and the females or queens lose their wings. At this time the females at- tempt to establish new colonies. Feeding habits vary with the species. Some feed on crops, fruits, seeds, nuts, and fungi. Others feed upon the exudate given off by plants or the honeydew ex- creted by certain insects. Those that feed on honeydew protect the insects that produce it. Still others feed upon the bodies of insects, small animals which they attack, or upon dead animals. Ants may injure lawns, gardens, and orchards by their nesting habits. Some species are attracted into a house by the presence of sweets or fatty substances. The most annoying ant in California is the Argentine ant, Iridomyrmex humilis Mayr, which has spread over most of the state since first found in 1905. It is very aggressive and, where strongly estab- lished, has driven out and largely re- placed many of the native species. The preparation of this section was made pos- sible through the splendid help of E. O. Essig, Professor of Entomology and Entomologist in the Experiment Station, Emeritus, who not only furnished much of the subject matter, but also numerous photographs. CONTROL: A number of insecticides are extremely effective. The two most effective are chlordane and dieldrin. Lin- dane is also effective and is sometimes available in combination with chlordane or dieldrin in commercial mixtures. These are available as dusts, sprays, and granules. The satisfaction obtained with these materials is dependent upon the thoroughness with which they are ap- plied. In making applications follow carefully the directions given on the con- tainers. The red harvester ant is also a problem in some of the drier regions. It can destroy garden plants as well as inflict painful stings. These ants are best con- trolled by dusting or spraying dieldrin or chlordane over the entrance to the nest and working it into the soil. BRACHYRHINUS WEEVILS Several species of Brachyrhinus wee- vils are very destructive to garden plants. The adults, depending upon the species, are shiny brown to nearly black and measure in length from about V± to a little more than % inch. They are true weevils, with heads terminating in a blunt snout. The larvae are white, cres- Both larvae and adults of Brachyrhinus weevils attack many ornamentals. [13] cent-shaped, legless grubs with brown heads; they are about J /2 inch long when mature. Both the adults and larvae are destruc- tive. The adults feed at night and hide during the day. Their typical way of feeding is to eat out notches along the edge of leaves. The larvae live in the soil and damage plants by feeding on the roots, underground stems, and the bark of the trunk just below ground level, thus girdling the plants. Plants attacked and often killed include bush berries, straw- berries, begonias, cyclamen, privet, many ornamentals such as camellias, rhododen- drons, azaleas, primroses, and wistarias. CONTROL: This is directed mainly against the adults, before they have had opportunity to lay eggs. The new genera- tion of adults usually makes its appear- ance in late April or May. At this time many can be killed by poison bait scat- tered in the garden. The most effective bait is a proprietary one consisting of a poison on dried apple pulp. The bait should be scattered at the rate of from 50 to 75 pounds to the acre or 1.25 to 2.5 pounds per 1,000 square feet of garden. Although not so effective, a substitute bran bait containing sugar, and poisoned with calcium arsenate or sodium fluo- silicate can be used. DDT, applied in a spray or as a 5 per cent dust, is an effective treatment which is used against the adult weevils. Infested plants can be sprayed or dusted, or the soil beneath the plants can be treated. Treatment should be timed in early spring when the adults are emerging from the soil but before they have had opportunity to lay eggs. Follow the direc- tions given on the package and use care not to contaminate vegetation meant for human or animal consumption. If Brachyrhinus weevils are a continu- ous pest, it is best to treat the soil with chlordane, aldrin, dieldrin, or heptachlor before planting. Apply one such insecti- cide in sufficient water to treat 1,000 square feet: chlordane, ^2 pound wet- table powder or 1 pint 50 per cent emul- sion; aldrin or heptachlor % pint 25 per cent emulsion; or dieldrin, V 2 pint of 15 per cent emulsion. If applied thoroughh and worked into the soil for 6 to 8 inches these materials will control larvae of the weevils for two to three years. BRISTLY ROSE SLUG r> „ j.ni The pale green bristly rose slug is a pest of almost every rose garden. The adult of the bristly rose slug is a small black sawfly which is related to bees and wasps. It is about % inch long, and lays its eggs in grooves in the midribs of the leaves. The caterpillar-like larvae are pale green, and when full grown measure about % inch in length. All in- jury is done by the larvae. They are found on the underside of the leaves which they first skeletonize; later they eat holes into or entirely devour the leaves. There are at least two generations STOMACH POISONS FOR CHEWING PESTS I 14] of slugs a year and the adults first appear in April or May. If not controlled, the pest may defoliate roses. CONTROL: This should start as soon as injury to the plant is noted. The pest is easily controlled with a spray or dust of any of the common stomach poisons. It is also controlled with DDT or DDD, methoxychlor, or lindane, but to avoid a serious increase in red spiders these in- secticides should be used in combination with sulfur or Kelthane. Most of the con- tact insecticides are effective in killing the rose slug if the pest is contacted with the material. Even nicotine is effective if applied when the larvae are tiny. BULB FLY Careful selection of firm bulbs is the best pro- tection from the bulb fly maggot. The bulb fly is a large hairy black fly, marked with gray, yellow, or orange, and is about % to % inch long. It greatly resembles and acts like a small bumble- bee. The eggs are small, oval, white, and are laid near the surface of the soil close to the crown of the host plant. The mag- gots when mature are robust, measure V2 to % inch in length, and are white, yellowish, or brown. The young maggots bore into the bulb and feed upon the tissue with their strong hooked mouth parts. This usually results in hollowing out the center of the bulb, or reducing it to a thick brown excre- mentaceous mass. Usually only a single maggot is found in a bulb. Narcissus bulbs are preferred, but amaryllis, hya- cinth, eurycles, galtonia, habranthus, hippeastrum, lilies, tulips, and vallota are attacked. Infested bulbs can be detected by pressing to determine their solidity. CONTROL: This is a difficult problem for the home gardener. Every attempt should be made to select and plant bulbs that are firm and free from maggots or injury. Commercial control is obtained by treating harvested bulbs in hot water for 2 hours at 110° F. The temperature must be accurately controlled because a temperature rise of a degree or two even for a short period is likely to injure the bulbs seriously. Field control is possible. Some relief ordinarily can be secured by treating the plants and the soil about them, following the blooming period, with sprays or dusts containing chlor- dane, dieldrin, heptachlor, or aldrin. Be- cause the flight period of the adults lasts through late spring and early summer a second treatment in late May and early June may be desirable. Treating the bulbs with a chlordane or heptachlor dip for 10 minutes before setting out the bulbs results in excellent control of the pest. A chlordane dip should contain 1% ounces of an emulsifiable concentrate containing 4 pounds of chlordane per gallon in 1 gallon of water. A 2 pound per gallon emulsifiable heptachlor con- CONTACT INSECTICIDES FOR SUCKING PESTS [15] centrate should be used at the rate of 0.6 ounce per gallon of water. To prevent the spread of basal rot, add sufficient Cercsan to make a 2 per cent mixture. CABBAGE WORMS Cabbage worms include three kinds that seriously injure cabbage and related plants : ( 1 ) The cabbage worm is the im- mature form of a white butterfly with dark markings; it is uniformly velvety green and, when full grown, is about 1 inch long. (2) The cabbage looper — the caterpillar stage of a moth — is light green, with several longitudinal fine white stripes running the length of the body. It grows to a length of about 1 inch. In crawling it loops its body — hence the name. (3) The caterpillar of the diamond-back moth is light green. It is the smallest worm attacking cabbage; when full grown it measures about V' inch. All three species eat irregular holes in the leaves of cabbage and related plants: in heavy infestations the plant is left worthless. Control: During early stages of plant growth, dust with DDT, DDD, or calcium arsenate. Do not use these above-named poisons after the edible parts of the plant have started to form; instead, thoroughly apply a dust containing at least 0.50 per cent rotenone, or a rotenone dust corn- Cabbage worms must be controlled during early stages of plant growth. bined with pyrethrum, nicotine, or or- ganic thiocyanate, or a spray or dust containing malathion. This latter insecti- cide should not be applied within a week of harvest. For satisfactory results, all of these materials should be applied be- fore the worms are large. Destroy cab- bage and related plants as soon as harvesl of that crop is completed. The worms attacking this group of plants are most serious in summer and fall. CORN EARWORM The corn earworm is about 1% inches long when fully grown. It ranges from green to almost black and may be marked with longitudinal stripes of various colors. It is principally a pest of fruiting bodies, into which it bores. It is the common worm found eating its way down through the kernels of the ears of corn. Also a serious pest of tomatoes, it usually enters at the stem end and consumes the inside of the fruit. It also attacks beans and many other crops and weeds. There are no less than three genera- tions in a year. The adult moths become active at about dusk, at which time females may be seen flitting here and there, laying eggs on their host plants. The eggs are laid mainly on the silk of sweet corn, while on other crops, such as tomatoes and beans, they are laid on the outer portion of the plant. The eggs are laid singly. They are pearly white when first laid but darken as they ap- proach the hatching of the young cater- pillars. CONTROL: On corn, the corn ear- worm mav be effectivelv controlled with a 5 per cent DDT dust. The DDT should be applied to the silk with a brush. The brush is dipped into the DDT. then pressed against the silk and given a twist to force the dust into the entrance of the silk channel. Treatment should be started within three davs after the silk appears, and repeated at least three times at three- day intervals. Each ear should be treated every time. Because of the residue from [16 The corn earworm not only likes corn, but will invade the tomato patch. DDT, do not feed corn stalks to animals if DDT has been used. Another method of control is by injecting directly into the silk channel 1 cubic centimeter (about !/4 teaspoon) of a highly refined mineral oil, which contains 0.2 per cent pyreth- rins. You can purchase this mixture from dealers handling insecticides. Oil interferes with fertilization; therefore, should be applied only after the silk has begun to wilt and turn brown. Use a plunger type of oil can. A setscrew at- tachment can be fitted to the plunger to regulate the amount of oil ejected with each stroke. Insert the nozzle of the oil can not more than % inch into the silk channel. For small plantings an ordinary medicine dropper can be used. Control can also be obtained by clipping off the tips of the ears to remove the entering worms. This should not be done until pollination is complete. Destroy clipped tips. On tomatoes, dust the plants lightly but thoroughly as necessary with DDT, DDD, or calcium arsenate. However, do not use DDT on tomatoes grown under glass. If treatment is required during the harvest season, wash or carefully wipe the fruit lo remove any poison residue. ( See to- mato mite.) CRICKET The common field cricket is a large, brown to black, swift-moving insect with long feelers. Nocturnal in habits, the cricket breeds in uncultivated areas; in high populations they may migrate to gardens in sufficient numbers to do some damage. The cricket feeds on foliage and with certain plants, such as tomato, at- tacks the fruit as it begins to ripen. CONTROL: The cricket is most suc- cessfully controlled with insecticides that contain dieldrin, heptachlor, or chlor- dane. Avoid applying these insecticides to parts of plants intended for human consumption, unless the residue can be removed by washing, wiping, or strip- ping. In applying the materials, carefully follow the directions given on the con- tainer label. Pellets or granules of these materials spread in and around the garden are also effective in controlling this insect. These do not leave a harmful residue problem of spray or dust. Even so, care should be exercised to see that they are not directly applied to edible portions of plants. Baits made of these materials are also effective but are limited in usage because they are attractive to the pest only while moist. Again avoid apply- ing bait to edible parts of plants. CUCUMBER BEETLES The western spotted cucumber beetle (or Diabrotica) is small and green, with twelve black spots on the wing covers. It is widespread throughout California and attacks most vegetables and many flowering plants, but particularly cucum- bers, squash, melons, beans, corn, and similar crops. The whitish, wormlike larvae feed on the roots; the adults on the leaves, stems, and floral parts. A close relative, the striped cucumber be:tle, is somewhat smaller. It is yellowish with three black lines down its back. It seri- [17] This small green cucumber beetle with its black spots is to be found in most gardens. ously attacks cucurbits (squash, melon, and the like) . CONTROL: When there is no residue problem, cucumber beetles can be con- trolled by thoroughly dusting the plants with DDT, malathion, dieldrin, hepta- chlor, or aldrin. However, DDT, dieldrin, aldrin, and heptachlor may occasionally cause some injury to certain varieties of squash. When a residue problem is in- volved, use malathion as a dust or a spray. The use of DDT, dieldrin, heptachlor, aldrin, and chlordane is likely to result in a serious increase of red spiders. The ad- dition of sulfur to the commercial dust will help to suppress red spiders but be- cause of the danger of injury do not use it on melons or strawberries. CUTWORMS or ARMYWORMS Cutworms or armyworms are the cater- pillars of moths. When full grown they are 1% to 2 inches long. Most species are somber in color, although some, such as the western yellow-striped armyworm, are rather showy. Cutworms attacking vegetables may be divided into two groups: (1) those feeding at night and hiding during the day in the soil and debris, and (2) those spending their entire larval life on the plant and feeding in the daytime. Cutworms cause injury by cutting off seedlings or newly transplanted plants below or above the ground, or by eating large, irregular holes in the leaves or fruiting bodies of older plants. CONTROL: Cutworms belonging to group 1 can be controlled with commer- cially prepared poison baits. Scatter the bait over the infested area just before dusk. To control cutworms belonging to group 2, dust the plants thoroughly with DDT, DDD, toxaphene, cryolite, or cal- cium arsenate. Where seedling stands are being injured by worms of either group, dust with lindane, DDD, DDT, or toxa- phene. Do not use toxaphene on melons or squash. The use of DDT, DDD, or toxaphene may result in a serious in- This cutworm is typical of the group that feeds at night and hides during the day. The yellow-striped armyworm is one of the cut- worms which feed during the day. [18] crease of red spider. The addition of ^4 to y 2 by volume of sulfur to the dust will help control this pest. Note precautions given for poison residues. EUROPEAN EARWIG The European earwig is a dark chest- nut-brown insect about % inch long, with a pair of forceps on the rear end of the body. Although provided with short wings, it usually runs. It feeds at night, and hides by day under boards, rocks, rubbish, and in crevices. It attacks many different kinds of vegetables, fruits, and flowering garden plants, eating holes in leaves and flowers. It is an introduced species not yet spread throughout the state, and is most destructive in the cooler coastal regions. Eggs are laid from De- cember through February, and the pest is most destructive from April through July. CONTROL: To control the European earwig, use a poison bait containing bran, sodium fluosilicate, and fish oil. Commercial prepared baits are available. Baits are most effective when used during April to July inclusive and should be ap- plied in the evening. The bait should be scattered over areas frequented by the pest but it must be kept off the plants. Since it is poisonous, it should be kept away from animals. A dust containing chlordane, lindane, dieldrin, aldrin, or hepiachlor is effective. Apply dusts around the hiding places of the earwig particularly along fences and house foundations. Avoid dusting the shrubbery heavily with DDT, dieldrin, aldrin, and hepta- chlor; these chemicals are known to kill beneficial insects that help to control other pests. Some insecticides such as dieldrin, heptachlor, and chlordane are prepared in granular form, which greatly facilitates their application and prevents serious contamination of foliage. When spread over the ground area where the earwigs hide these insecticides are very effective. Avoid applying granules to edible parts of plants. FLEA BEETLES Flea beetles are small and are black, brown, greenish, or yellowish. Most of them are only about % 6 inch long. They jump like fleas and eat small holes in leaves. Many species attack vegetables. Where infestations are heavy, plants may be nearly defoliated. Seedlings or newly transplanted plants are likely to be most seriously injured. The minute wormlike grubs feed upon roots and tubers of cul- tivated and wild plants. t ** Great numbers of earwigs may be found under boards or rubbish, and should be baited, or the infested area dusted. Tiny flea beetles eat small holes in leaves and can defoliate a plant. [19] CONTROL: To control flea beetles, dust the infested plants evenly and thoroughly with DDT, lindane, methoxy- chlor, dieldrin, aldrin, heptachlor, cryo- lite, or calcium arsenate. Where a residue problem is involved, use 0.75 per cent rotenone dust. Note precautions on page 3. GARDEN CENTIPEDE or GARDEN SYMPHYLID (Not an insect but has chewing habits and is controlled by the same methods used for chewing insects.) The adult of the garden symphylid — which is centipede-like in appearance — measures about ^4 mcn m length. They are delicate and a uniform light cream color except for a darker streak caused by the contents of the digestive tract. The garden centipede lives in the soil, is rapid in movement, and may penetrate the soil to a depth of 3 feet or more. They feed on the roots and tubers of most plants and, under moist conditions, may come to the surface of the soil and feed on the under surfaces of leaves that are in con- tact with the soil. Where abundant they may destroy germinating seeds and trans- plants and seriously attack the roots of established plants. Where this latter situa- tion occurs the infested plants may be stunted and show lack of vigor. CONTROL: Because they live in the soil, the garden centipede is difficult to control. Some relief can be obtained by spreading lindane over the soil and work- ing it in to a depth of 6 inches. The treat- ment is best applied two to three weeks before planting. Lindane must be used with some caution because it imparts an off-flavor to some crops, such as potato and root crops. Some suppression of the garden centi- pede or garden symphylid population can also be secured where capsules of ethy- lene dibromide are used as a soil fumi- gant. These are commercially available, and the directions given on the package should be followed carefully. The garden centipede is unable to make its own runways and for this reason firm- ing the soil about transplants helps in getting the plant established. GRASSHOPPERS Grasshoppers are familiar garden pests in the warm interior areas of California. The young are much like the adults except that they do not have fully developed wings. In growing they cast their skin a number of times. With each cast they gain in size and the wings become more apparent. The fully developed adult ap- pears after the final molt. Eggs are laid in the soil but do not hatch until the following spring. Both young and adults attack plants. Young plants may be eaten off. When in- festations are severe, large plants are de- foliated and even the tender bark may be eaten from trees and ornamentals. CONTROL: Grasshoppers are con- trolled by scattering commercially pre- pared poison bait lightly over the infested area in early morning. Repeat the opera- tion at intervals of a few days to a week until the pest is eliminated. Dieldrin, al- drin, heptachlor, lindane, and chlordane dusts or sprays are effective. <0fr ^ : ^ v >: - : mm »* nv • -x Grasshoppers feed on vegetables as well as on the leaves and tender bark of many plants. 20] HEPIALID MOTH The larvae of this moth when mature measure about IV2 inches in length. They attack the roots of many ornamentals and in the region adjacent to the San Francisco Bay rank as one of the most destructive pests of garden plants. Their damage to plants is often attributed to other soil-infesting insects, such as the larvae of Brachyrhinus weevils. The larva of the hepialid moth eats, girdles, and bores through roots and the crown of plants below the soil surface. Among the plants that may be attacked and fre- quently killed are azalea, camellia, rho- dodendron, rose, and many other plants. CONTROL: Despite the serious and widespread damage done by the pest, little is known about its control. Spray- ing the base of plants with DDT might give some relief, but to the present time no experimental data support this con- tention. HORNWORMS Hornworms (tomato and tobacco) are caterpillars of the large "sphinx" or "hummingbird" moths. When fully grown they are nearly 4 inches long. They are predominantly green, with white diag- onal stripes, and with a characteristic spine (horn) at the rear end. They are serious pests of tomato, on which they feed upon the vine, blossoms, and fruit. Hornworms are most destructive in the warm interior valleys. If left unchecked they may completely defoliate plants. They also attack potatoes, eggplant, and peppers. A favorite wild host is the Jim- son weed. CONTROL: These are controlled best by hand-picking and destroying them as soon as they are seen. They are found most easily in early morning, when feed- ing is confined largely to the outside of the vine. DDD, DDT, or calcium arsenate dusts are effective. Dusting must be light but thorough. If the application is made dur- ing the harvest period, wash or carefully wipe the tomatoes, eggplants, or peppers to remove any poisonous residue. On to- matoes, if the tomato mite is present, use a dust containing 50 to 75 per cent sulfur. LAND PLANARIANS (Not an insect but has chewing habits.) Along the coastal areas of middle and northern California and particularly in the San Francisco Bay region, there are two species of these peculiar, shiny flat- worms that somewhat resemble slugs ex- cept that they are much more slender, flatter, and do not have horns. Like slugs, they travel on a slime path. The larger of these is a yellowish species which may attain a length of 3 inches, and the smaller one is black and only about 1% inches long when mature. They are most often found feeding on and in the fruit of strawberries of which they are very fond. Under moist conditions they may become numerous and do much damage. CONTROL: Less frequent watering helps to reduce their numbers. They dis- appear as summer approaches. The big green hornworm enjoys vegetables. He can be found most easily in early morning on tomato, pepper plants, eggplant. LEAF MINERS Many kinds of leaf miners attack vege- tables, flowering plants, and ornamentals. Most leaf miners are the larvae of flies. When hatched from eggs which have been laid on the surface of the plants, the min- ers, or small maggots of the spinach leaf miner, enter the leaf tissues and feed be- tween the two surfaces. They cause large, colorless blotches or mines. Where nu- merous they may destroy the entire leaf. On holding infested leaves to the light, you can easily see the maggots in the mines. The beet or spinach leaf miner is whit- ish and when full grown is nearly % inch long. Spinach, beet, and chard are among the plants seriously injured. Numerous other leaf miners attack gar- den plants. These are much smaller than the spinach leaf miner. The adult flies in- sert their eggs into the leaf surface and, on hatching, the larvae or maggots make a serpentine type of mine in the leaves. Under conditions of severe infestation plants may be defoliated. CONTROL: Late fall and winter-grown crops usually escape injury from leaf miners. Spring and summer crops are sometimes seriously attacked. Control of leaf miners with insecticides is difficult. The most effective materials are dieldrin, heptachlor, and aldrin. Because of a resi- due problem these materials cannot be used on leafy vegetables, especially spin- ach. However, they can be applied to to- mato and eggplant, and to flower plants and ornamentals at any time. When a res- idue problem is involved on edible plants, a nicotine spray containing 1 teaspoon of nicotine sulfate and 2 tablespoons of soap to 1 gallon of water, if applied frequently, is partially effective. LEAF TIERS and LEAF ROLLERS The adults are small, somber-colored moths that measure about % inch in length when at rest. Depending upon the species the caterpillars are various shades of yellow, tan, or green with amber-col- ored heads. When mature the caterpillars are about % incn in length. According to the species involved, they feed within leaves that are tied together with webbing or in a leaf-fold that is held in place by webbing. Besides feeding on the leaves, they attack developing buds and fruiting bodies. The caterpillars of leaf rollers wriggle violently backward when dis- turbed. They move into their leaf-roll shelters or they may drop to the ground on a silken thread. Upon reaching maturity the caterpil- lars pupate within the parts of the plant that have been webbed together. After a period of time the adults emerge and, ac- cording to the species, lay eggs singly or in batches either on the stems or more often on the undersides of the leaves. CONTROL: Best results with insecti- cides are obtained if treatments are ap- plied while the caterpillars are still small. The colorless area in the leaf at the left is caused by leaf miners which feed between the two leaf surfaces. At right the mining operations are exposed. [22] Insecticides containing DDT, DDD, lin- dane, cryolite, pyrethrum, malathion, or a combination of these materials should effectively control the pest. MILLIPEDES (Not an insect but has chewing habits.) Millipedes are long, wormlike animals related to centipedes, but differing from centipedes in that they have two pairs of legs on each body segment, except for the first three segments behind the head. The common forms, found in gardens, have hard bodies, measure from % to 1 inch long, and are dark brown or cream- colored. The bodies of some species are round — others are somewhat flattened. They are active at night but during the day they hide in secluded locations, un- der boards, rocks, and flats. If their hid- ing places are disturbed they can often be seen coiled in a very characteristic man- ner. Millipedes like damp locations and are found in greatest abundance in moist spots that are rich in organic matter. Their food is supposed to consist of de- caying vegetation, although where they are extremely abundant, they may feed on growing vegetation. On occasions, they have been known to feed on sprout- ing seeds, tubers, and bulbs. CONTROL: Control measures are sel- dom justified unless millipedes are pres- ent in large numbers. Dust or sprays con- taining DDT, chlordane, dieldrin, mala- thion, lindane, or combinations of these materials are partially effective in con- trolling the pest. These materials should be used accord- ing to the manufacturer's recommenda- tions, and should be applied to the areas frequented by millipedes. Although the treatment is rather expensive, millipedes can be controlled by thoroughly wetting the soil about the infested plants with a 40 per cent nicotine sulfate solution, di- luted at the rate of 2 teaspoons to the gallon of water. PEA WEEVIL The pea weevil is a short, chunky beetle about % inch long. The base color is brownish, flecked with white, black, and gray patches. There is a distinct spot of white scales just back of the head, and another on the exposed tip of the abdo- men. The adults leave their hibernating quarters in the spring and fly to the peas coming into bloom. They are attracted to the flowers, because they must feed on pollen before they are able to lay eggs. The tiny, long, yellow or orange-colored eggs are laid on the developing pea pods. The larvae or grubs upon hatching bore directly through the egg shells and pod and enter the developing peas. Except for the first stage, the larvae are legless, grub- like, white with a brown head. The entrance made by the larvae into the peas is very small and difficult to de- tect. The larvae complete their develop- ment inside the peas in from 30 to 50 days. After constructing a tunnel to the seed coat so that the adults can more readily emerge, the larvae pupate. After 10 to 15 days the pupae transform to the adult beetles, which escape from the peas by cutting out a circular hole in the seed coat. There is only one generation a year and, unlike the several species of bean weevils, the pest does not breed in stor- age or in dry peas. ^ y£i ^SL# \ ^ ^ These insects entered the peas as larvae and now emerge as full-grown weevils. [23] CONTROL: The pea weevil can be controlled by thoroughly dusting the pea vines with a dust containing 5 per cent DDT. Not more than two applications are necessary : the first should be applied shortly after the start of bloom; and the second at the height of the blooming pe- riod. Where DDT is applied, do not feed the treated pea vines to livestock. As a sanitary measure, destroy the pea vines as soon as harvest is completed. A dust containing 0.75 per cent rotenone is also effective. Apply the treatment at weekly intervals from shortly after the begin- ning until the end of the blooming period. ROOT MAGGOTS Root maggots include several species that seriously attack the roots of grow- ing plants. The maggots are the larvae of flies; they are legless, without distinct heads, and are nearly white. They bore into the germinating seeds and roots, and often make difficult the growing of cer- tain vegetables. There are three impor- tant species: (1) The cabbage maggot attacks cabbage and related crops. It is serious in summer. (2) The seed-corn maggot attacks germinating seeds and roots of corn, beans, peas, tomatoes, and other crops. It is particularly serious where the soil is moist and cold; and it is usually most active early in the sea- son. (3) The onion maggot attacks on- ions, shallots, garlic, and related crops. CONTROL: To control the cabbage maggot, place disks of tarred paper about the plants at the ground level and in close contact with the soil at the time of transplanting. The disks should be about 3 inches in diameter, with a hole in the center and a slit to facilitate plac- ing them about the stem of the plants. Dichloroethyl ether has proved effective. It is available in commercial ready-mixed preparations, which may be added to water at the rate of 1 to 400, or 2 tea- spoons to the gallon, and applied with sprinkling can to the soil around the plant at the rate of 1 cupful to a plant or 1 cupful to 8 inches of row. To avoid injury from the seed-corn maggot, particularly to beans and corn, delay planting until the soil warms up. To avoid injury from the onion maggot, spray the soil about the plants with 2 parts of a highly refined oil emulsion to 100 parts of water. Destroy cull onions as soon as harvest is complete. Most ef- fective control of root maggots can be obtained with chlordane preparations. Soil application of chlordane, dieldrin, or heptachlor before planting, or dusting the transplants before setting out is also helpful. Follow manufacturer's recom- mendations. The seed-corn maggot is best con- trolled by using treated seed where this is available. SNAILS and SLUGS (Not insects but have chewing habits.) All gardeners know the domage done by snails and slugs. They feed chiefly at night, and frequently cut off young plants. Poison bait is the best control. [24] Snails and slugs are so well known to nearly everyone that detailed descriptions are not necessary. The former have shells, the latter do not. Both have chewing mouth parts and feed chiefly at night. They attack many kinds of plants and often leave slime tracks upon the plant on which they have fed. CONTROL: Snails and slugs are best controlled with poison baits that contain both calcium arsenate and metaldehyde. Such baits are available as commercial products and are obtainable from almost any dealer selling insecticides. Best re- sults are obtained by scattering the bait in the evening on wet ground. Dusts containing 10 per cent metaldehyde give satisfactory control, as does dusting plants with calcium arsenate. Do not apply these poisons to edible parts of plants unless the residue can be removed. Many of the pests can be destroyed by hand-picking. SOD WEBWORMS or LAWN MOTHS The two lawn-infesting insects are the fawn-colored lawn moth and the silver- barred lawn moth. The adults are small. The forewings of the fawn-colored lawn moth are brown, variegated with buff, white, and black; those of the silver- barred lawn moth are golden with a long- itudinal silver stripe. These pests breed continuously throughout the late spring, summer, and early fall. The adults fly slowly over lawns at dusk while scatter- ing eggs in the grass. All damage is done by the caterpillars which hatch from the eggs. The caterpillars when full-grown are about % inch in length and are gray- ish with black spots. Serious damage is done to bent and bhiegrass and other grass lawns during the summer and early fall. The crowns and new buds are attacked, which causes irregular brown spots in the lawn. Dam- age by these insects might be confused with the lawn diseases causing brown patch and dollarspot, but the insect dam- age can be distinguished by unevenness of grass height and irregularity in the shape of dead spots. Accurate determination of infestation can be obtained by wetting the sod about the dead areas with a pyrethrum solution. Use a commercial pyrethrum prepara- tion that contains 2 per cent pyrethrins, diluted with water at the rate of 1 part to 400 (2 teaspoons to the gallon), and apply to the grass by means of a sprin- kling can at the rate of 1 gallon to the square yard. Any webworms present will come wriggling to the lawn surface. A serious infestation is indicated if at least 100 individuals per square yard come up within 10 minutes. From top to bottom, the adult and the larva of the fawn-colored lawn moth; the adult of the silver-barred lawn moth with the bar show- ing conspicuously in this profile view; the larva of the silver-barred species. [25 CONTROL: A number of insecticides are effective in controlling sod web- worms. Pyrethrum products and dichlo- roethyl ether at proper dosages result in a good kill of the caterpillars present, but have no residual action, and the lawns are subject to reinfestation right after treat- ment. However, some residual action can be obtained if dichloroethyl ether is used in combination with lindane. If these materials are used, follow the directions given on the container. A spray contain- ing 2 ounces, by weight, of actual DDT, chlordane, or toxaphene, or 1 ounce by weight of aldrin, dieldrin, or heptachlor is very effective in controlling lawn moths. The amount of insecticide sug- gested, when diluted with enough water, is sufficient to control the worms on 1,000 square feet of lawn. Another very satis- factory treatment to prevent reinfestation, is to spray the lawn with a standard lead arsenate spray. The standard lead ar- senate is used at the rate of 5 pounds to 50 gallons of water. This amount is enough to treat 1,000 square feet. The mixture is best applied with a sprinkling can, and the spray should be allowed to dry before rewatering. Lead arsenate is very poisonous and every effort should be made to keep it off vegetation which is intended for either human or animal food. Granules which contain dieldrin and lindane are effective if they are evenly scattered over the lawn. In us- ing any of the above treatments care- fully follow the directions given on the containers. In no instance should chil- dren or pets be allowed on the lawns until the insecticides have been watered into the grass and the lawns given an op- portunity to dry. SOWBUGS and PILLBUGS (Not insects but have chewing habits.) ^Pi r '"9t The dooryard sowbugs live in moist, damp places. Sowbugs and pillbugs are dark gray or slate colored, with chewing mouth parts. They are somewhat flattened, have seven pairs of legs, and move rather slowly. They breathe by means of gills and therefore must live in moist, damp places. Unless present in large numbers, they are seldom destructive. They are, however, particularly injurious to seed- lings. Pillbugs can be distinguished from sowbugs in that they curl up into a round ball when disturbed. CONTROL: Sowbugs and pillbugs can be controlled by dusting the infected ground with a calcium arsenate flour mix- ture. Thoroughly mix 2% pounds of cal- cium arsenate with 1 pound of white flour. This quantity of the mixture, thinly but evenly applied is sufficient to dust 700 square feet. This mixture is a poison and should not be applied to portions of STOMACH POISONS FOR CHEWING PESTS [26] leafy or heading vegetables which are to be eaten, nor to other vegetables after the fruit is set. Poison baits recommended for cutworms, snails, and slugs are partially effective. Baits containing dieldrin are most effective and granules containing both dieldrin and lindane give satisfac- tion. A 5 per cent DDT dust applied to their hiding places gives very effective control. Avoid dusting shrubbery; DDT and similar insecticides will kill beneficial in- sects that help to control red spiders and several other important pests. TOMATO PINWORM The tomato pinworm, the caterpillar of a tiny moth, is about % inch long when fully grown. The young worms are light pink, but the older ones appear as grayish purple. They attack all portions of the vine, but are most destructive to the fruit. They may enter it at any point, but usually they enter at the stem end and burrow into the core and the fleshy parts that radiate from it. The pest also attacks potato, eggplant, and nightshade. The area where the pinworm is likely to be a problem is limited to southern California and the central and southern San Joaquin Valley. CONTROL: This pest is controlled by a 5 per cent DDT dust or a cryolite dust thoroughly applied to the vines. In sea- sons when pinworms are serious, dust the vines first when the fruits are about the size of marbles. Apply two other dust- ings at 2-week intervals, and a fourth after harvest has started. Any dust on the fruit should be carefully washed or wiped away. If the tomato mite is also believed to be present, use a dust containing 50 per cent sulfur. VEGETABLE WEEVIL The vegetable weevil is a brown or buff-colored snout beetle measuring about % inch in length. The larvae are legless, light-green grubs that measure about V2 inch long when full grown. Both the adults and larvae feed on the foliage of a number of winter and spring vege- tables; the larvae also feed on vegetable roots, particularly of carrots and turnips. The vegetable weevil, which has spread to many parts of California, is particularly serious as a pest in the cooler coastal areas. It has not been reported as being a serious pest of flowering plants and ornamentals. CONTROL: As soon as the first larvae are seen, the infested plants should be treated thoroughly with a 5 per cent DDT dust, or a dust containing malathion. Use the same treatments for control of the *, v ' yV ■■•■• The fat grubs of the vegetable weevil destroy root vegetables, such as turnips. CONTACT INSECTICIDES FOR SUCKING PESTS [27] adults. If a residue problem is involved, use a 1 per cent rotenone dust. Poison baits can be effectively used against the adults but are not effective against the larvae. WIREWORMS Wireworms, the immature stages of "click beetles," have smooth, round bodies and tough skin. They are shiny and vary in color from pale yellow to dark brown. They live in the soil, pre- ferring lighter soil types. Most of the destructive species are not more than 1 inch long. Usually one to three years are necessary for wireworms to complete their development. Wireworms injure plants by cutting off roots, by boring into tubers and fleshy roots, or by penetrating into the root and up into the stems of plants. They may also seriously attack germinating seeds. CONTROL: They can be attracted to baits, such as carrots, which are placed in the moist surface soil and spaced 2V2 to 3 feet apart each way. If the tops are left on, the carrots can easily be pulled out every few days, the wireworms re- moved, and the baits put back into the soil. Chlordane, heptachlor, dieldrin, or aldrin applied and incorporated into the soil are most effective in the control of Wireworms live in the soil, and attack roots and germinating seeds. wireworms. The use of treated seed is also very effective in protecting against wireworm. Seed that has been treated by the producer should be purchased where available. The fumigant dichloroethyl ether in combination with lindane is highly effec- tive against wireworms. The fumigant ethylene dibromide also is an effective control. This fumigant is available in small containers for home gardens. It should be applied prior to planting. In applying any of the above treat- ments carefully follow the directions as given on the container. Sucking Pests APHIDS Aphids are small, fragile, soft-bodied insects with sucking mouth parts. Some have wings, others do not. They are black, green, yellowish, or pinkish, and their bodies are naked or perhaps cov- ered with a powdery wax. They live in colonies where they excrete quantities of honeydew which attracts ants and on which a sooty mold fungus grows. Many species attack vegetables and other gar- den plants, causing deformation and curling of leaves. If not controlled, they make the growing of certain plants very difficult. CONTROL: Aphids are controlled with contact insecticides containing mala- thion, lindane, nicotine, pyrethrum, ro- tenone, organic thiocyanate, highly re- fined mineral oil, or combinations of these materials. Because many of the aphids develop on the underside of leaves, thoroughness of application is one of the [28] The wingless species of aphids found in great numbers on many plants. most important factors in obtaining good control. For satisfactory results, spray or dust as soon as aphid colonies are ob- served. If you wait until after leaves are curled, control is difficult because the aphids are hard to reach with the spray or dust. Destroy infested plants as soon as harvest of that crop is complete. To prepare a nicotine spray use 1 tea- spoon nicotine sulfate solution and 2 tablespoons soap to 1 gallon water. Dis- solve the soap in a small quantity of warm water before adding to mixture. HARLEQUIN CABBAGE BUG The harlequin cabbage bug is black, with bright red and white markings on its back. It is about % inch long when mature. The immature forms are also highly colored. Both the adults and the Harlequin cabbage bugs must be killed, as they do severe damage. young injure plants by sucking the juice. The insect is a serious pest of cabbage and related plants. Feeding causes de- formation, accompanied by whitish or yellowish spotting of the leaves. In heavy infestations the affected plants wilt, wither, and die. CONTROL: The harlequin cabbage bug is very difficult to control. Every effort should be made to keep it from be- coming established. Wild radish and mustard are breeding plants and should therefore not be allowed to grow near a garden. Old cabbage, cauliflower, broc- coli, or other cruciferous plants should be removed, since they furnish breeding and hiding places. Hand-pick and destroy any bugs ob- served and also the egg clusters found usually on the underside of the leaves. A malathion spray or dust is partially effective against the young, but not against the adults. Malathion plus 5 per cent DDT gives some relief but this can be used only up to the time that the edible portions of the plant begin to form. A 0.75 per cent rotenone dust, thoroughly applied, is effective. A 10 per cent nico- tine dust, or a strong nicotine and soap spray is somewhat effective against the nymphs. LEAFHOPPERS Leafhoppers are slender insects with forewings thickened and often colored, and with minute bristle-like antennae. A number of species attack garden plants. The adults are yellowish green to green- ish and many species may have a definite color pattern. They range from about Vs to % inch in length. They are active jumpers, and the young have a char- acteristic habit of running sidewise. The adults are capable of rapid flight. The eggs are laid in the tender plant tissue. The young are wingless, pale-colored, and are generally found on the under surface of the leaves. Injury is caused by the insect piercing the plant and sucking out the juices. First evidence of attack is 29 Leafhoppers suck plant juices, and also carry virus diseases to many garden plants. a white stippling on the upper leaf sur- face. In cases of severe attack this is fol- lowed by drying up and death of the attacked tissue. Besides direct injury, leafhoppers are the carriers of a number of very important plant virus diseases. Among the garden crops that may be seriously attacked are potato, squash, beans, melons, rose, aster, and related crops. CONTROL: To destroy a sufficient number of leafhoppers to prevent the transmission of virus diseases in the gar- den is not possible. Sprays or dusts con- taining pyrethrum or malathion, if thoroughly applied to all surfaces of the foliage, are effective against those leaf- hoppers that cause direct damage. A 5 per cent DDT dust or a DDT spray re- sults in control, but may encourage an increase in the red spider population. Danger of red spider can be reduced if sulfur is incorporated in the dust. A DDT-sulfur mixture should be used with caution as sulfur is likely to cause serious injury to some kinds of melons and re- lated plants. DDT in combination with malathion also tends to suppress an in- crease in spider mites and aphid popula- tions. MEALYBUGS (Aerial) Mealybugs are among the most serious sucking pests of plant life. They are from Ys to 14 inch long, and have flattened, elongate, oval bodies covered with a white, powdery wax. This wax extends from the margins in a series of filaments, usually with two longer ones at the pos- terior end. They usually develop in colo- nies and are capable of slow crawling. They excrete large amounts of honeydew which not only attracts ants, but on which a sooty mold fungus grows. Breed- ing is most pronounced during the sum- mer and fall, although the pest occurs on the plants during the entire year. They continuously injure house plants and greenhouse plants of all kinds. The eggs, which are usually oval, pale yellow, or orange, are laid in cottony masses which may cover large areas of infested plants. Damage is done by the females. The mature males have abortive mouth parts and are tiny, white, two- winged insects with two conspicuous long Above is a typical species of aerial mealy- bug with white, waxy body, growing in a colony on a flower stalk. [30] filaments at the tail end. During the mat- ing season from near sunset to dusk on warm, bright days the males may be pres- ent in great swarms hovering in the air about plants infested by the females. CONTROL: Because of their waxy cov- ering and because many of them may feed upon the roots in the soil, mealybugs are difficult to control. Summer oil emul- sions, thoroughly applied to portions of plants aboveground are effective. They should be used at the rate of 1 to 1% gallons to 100 gallons of water (3 to 5 tablespoons to the gallon). To insure satisfactory results, the treatment should be repeated two or three times at inter- vals of one to three weeks. If other con- tact sprays are used, such as malathion, the directions on the containers should be followed. Nicotine-soap sprays are of little value unless used in combination with oil sprays. Best results with most contact insecticides are obtained when they are used in combination with sum- mer oil emulsions. Many mealybugs and their eggs can be removed by hosing them off with a strong stream of water. If this treatment is re- peated at intervals of every two to four weeks, the pests can often be held in check. MEALYBUGS (Soil) Ground mealybugs are very small; a thin covering of white, powdery wax makes their bodies almost white. They at- tack the roots of numerous plants includ- ing lawn grasses, practically all perennial Soil mealybugs may be found in masses around roots and are hard to control. shrubs, and many annual plants. Where an infestation is heavy, the soil about the roots of plants will contain white cot- tony masses. If these and the soil are carefully examined, tiny, slow-crawling mealybugs no larger than the head of a pin can be seen. Injury to plants is caused by the sucking out of plant juices, which weakens the infested plants. CONTROL: Soil mealybugs are very difficult to control. Where plants are growing, there is no highly satisfactory control. Where soil is known to be infested, control can be obtained by spading it and wetting it with dichloroethyl ether solu- tion. A dichloroethyl ether emulsion should be used at the rate of 3 teaspoons to the gallon of water and applied to the infested ground at the rate of 3% gal- lons to the square yard. The application should be made to moist soil, and should not be applied where plants are growing because the dichloroethyl ether is likely to injure them. Treated soil should not be planted for at least three weeks follow- ing the application. Some relief can be obtained by build- ing a basin about the base of infested plants and thoroughly wetting with a nicotine-soap solution. Nicotine sulfate should be used at the rate of 2 teaspoons to the gallon of water. This insect thrives in unmolested soils. Cultivation is a very effective remedy wherever it may be employed. Repeatedly spading and turning the soil to dry it out, or practicing summer fallowing will rid the areas of the pest. Mealybugs are readily brought into gardens on potted plants. Many plants tolerate soil mealybugs. Among these are African marigolds, cabbage, camellia, corn, dahlia, geranium, rose, stock, and SCALES (Armored) Armored scales, in general, are smaller than unarmored scales. Depending upon the species, they measure from about % 2 [31] A thick shell protects these armored scales which suck out plant juices. to % inch in diameter or length. They are protected by a thick shell or scale which covers the body, and range in color from nearly white or light gray to dark brown. The mature females may be oval, nearly circular, elongate, or oyster shell in shape. The male scales are much smaller and often cannot be seen at all. Most species are flattened, although some are rather strongly convex. The scales when newly hatched are active and move about freely, but after the first molt they lose their legs and become stationary. These scales injure plants by sucking the juice with their mouth parts, which are adapted for this purpose. Some spe- cies inject a toxic substance into the plant, evidenced by a staining of the tis- sue about the scale, or by a rapid death of that part of the plant attacked. Unlike the unarmored scales, little or no honey- dew is secreted. The pests are found most abundant on the stems and under surface of the leaves, although they may also occur on the fruit. There are from one to many generations a year, depending upon the species and the climatic conditions. CONTROL: On deciduous plants ar- mored scales can be controlled during the full dormant season, December to February, by thoroughly spraying with a winter or dormant oil emulsion, or even a summer oil emulsion, at the rate of 5 to 6 gallons to 100 gallons of water (16 to 20 tablespoons to the gallon). In the growing season and on evergreen plants, summer oil emulsion sprays applied dur- ing the hatching period at the rate of from 1 to 2 gallons per 100 gallons of water (3 to 6 tablespoons to the gallon) will control the pests. To insure satis- factory results, the applications should be repeated several times at 2- to 3-week intervals. The effectiveness of oil sprays can be improved by combining them with malathion or rotenone. Good control will be obtained if mala- thion is used in combination with sum- mer oil. For best results the directions as given for the summer oil emulsion should be followed. Frequent applica- tions of nicotine sulfate and soap follow- ing hatching give good control. When contact sprays are used follow the direc- tions given on the containers. A localized infestation on a plant can sometimes be removed by pruning. SCALES (Unarmored) Unarmored scales are small insects with sucking mouth parts. The outer wall of their bodies is thickened for protec- tion. There are many economic species, all varying greatly in shape. Some are The soft scales attack woody plants in particu- lar, and secrete quantities of honeydew. [32] oval and somewhat flattened, others oval and strongly convex, while others are nearly globular when mature. They are naked or partially covered with a pow- dery, waxy secretion. A few have an elon- gated, cottony egg sac. The young can move about freely, but become more ses- sile (or attached) with maturity. All species are entirely stationary when fully developed. Most species secrete large quantities of honeydew which attracts ants, and on which a sooty mold fungus grows. A wide range of plants is attacked. These scales are not a pest of vegetables or most annuals. Woody plants are chiefly attacked, and the scales are usually to be found in greatest abundance on the stems, branches, and under surface of the leaves. Some species pass through two or more generations in a year, with the winter spent in the immature stage. CONTROL: On deciduous plants, un- armored scales can easily be controlled in the dormant season by thoroughly spraying with a winter dormant oil emul- sion at the rate of 3 to 4 gallons to 100 gallons of water (8 to 12 tablespoons to the gallon). During this period the pest can also be controlled by spraying with malathion and oil. Malathion, how- ever, is not effective if applied in late winter after the scales have started rapid growth. No treatment of any kind should be attempted from this time on until the scales have completed their development and the eggs have hatched. During the growing season and on evergreen plants, summer oil emulsions may be used at the rate of 1 gallon to 100 gallons of water (3 table- spoons to the gallon), or other contact sprays such as malathion at the dosage recommended by the manufacturer. To insure satisfactory control in summer apply treatment after the eggs have hatched. If there is an uneven hatch a second application may be desirable. In a localized infestation some relief can be obtained by pruning out the seriously infested portion of the plant. SPIDER MITES or RED SPIDERS (Not insects but have sucking habits.) Spider mites or red spiders are barely visible to the naked eye. Their color varies from very pale yellow to orange, red, and greenish. Some species spin much webbing and are usually abundant on the undersides of leaves. They suck the cell sap from the surface tissue of plants. In severe infestations there is first a fine white stippling, then a yellowing of the infested parts, followed by com- plete destruction of the tissue. They do most damage during the warmest part of the year. CONTROL: The most effective mate- rial for the control of spider mites is Kelthane. Excellent control can also be obtained with Aramite, but this material cannot be applied to any product used for human food. If either of these mate- rials is used, carefully follow the direc- tions given by the manufacturer on the container. In California in the warm interior val- leys, spider mites can be suppressed by thoroughly and evenly treating the in- fested plants with dusting sulfur. In the cooler coastal regions it may be necessary to spray with a 1 per cent light summer oil emulsion. The lower as well as the Stippling of the leaves is typical red spider damage. The tissue will then die. [33] upper surfaces of the leaves must be thoroughly wet with the spray to insure satisfactory control. Infested plants should be destroyed as soon as harvest of that crop is complete. Indiscriminate use of DDT, DDD, lindane, and diel- drin has resulted in serious increases in spider mite populations. The addition of ■/4 to % DV volume of sulfur to the com- mercial dust product will help control as well as prevent a buildup of this pest. Malathion sprays are effective in killing spider mites, but are not effective against the eggs, and so a second spray should follow after the eggs hatch, in 7 to 10 days. SQUASH BUG The squash bug is hard to control, and both adults and eggs should be destroyed. Squash bugs are grayish-brown, some- what speckled, sucking insects nearly % inch long when mature. The visible mar- gin of the abdomen as seen from above is orange or alternately striped orange and brown. The young at first are pale green with pinkish legs and antennae. Later, the forepart of the body is dark, and the rest becomes a pale grayish brown. The shining brown eggs are usu- ally laid in clusters on leaves and stems. Both the adult and the young suck the juices of plants. In serious infestations the plants wilt and die. These bugs are a serious pest of cucumbers, melons, pump- kins, squash, and related plants. CONTROL: The squash bug, like the harlequin cabbage bug. is difficult to con- trol; every effort should be made to keep it from becoming established. The adults and eggs should be promptly hand-picked and destroyed. Squash and other host plants should be destroyed as soon as the harvest of that crop is complete. Spraying with a strong nicotine and soap spray (2 to 3 teaspoons of nicotine sulfate to a gallon of water in which 2 or 3 table- spoons of powdered soap have been dis- solved), or dusting with a 4 per cent nicotine dust (10 per cent nicotine sul- fate) kills many of the very young, but not the more mature and adult bugs. Pyrethrum dusts containing at least 0.2 per cent pyrethrins are somewhat effec- tive against the young bugs. A thorough treatment with malathion is somewhat effective against the small nymphs. THRIPS Thrips are small, slender insects, pale to nearly black, with mouth parts con- structed primarily for sucking. They are about Y2-) inch long and usually have two pairs of fringed wings, carried length- wise over the back. Both the adults and the nymphs, or immature forms, of most species do damage. Their rasping and puncturing of the surface plant cells cause silvering of the leaves, fruit, and stems. Thrips have a habit of feeding in colonies. Attacked surfaces frequently be- come deformed, dry. and may drop. CONTROL: Malathion dust or sprays are very effective against thrips, as are DDT and toxaphene dusts and sprays or mixtures that contain lindane or dieldrin. STOMACH POISONS FOR CHEWING PESTS [34] DDT, lindane, toxaphene, or dieldrin should not be applied to portions of plants intended for human consumption unless the residue can be removed. When these materials are used, carefully follow the directions on the container. A nicotine soap spray at the rate of 1 teaspoon of nicotine sulfate solution and 2 table- spoons of soap to 1 gallon of water can be used. Thorough application is neces- sary. The treatment should be repeated every 10 days until the pest is held in check. Destroy infested plants as soon as harvest is complete. TOMATO PSYLLID The tomato psyllid is related to aphids. It is approximately the same size as the latter and the adults resemble miniature cicadas. The eggs are very small, yellow, and are attached to the leaves by means of a short stalk. All damage is done by the scale-like nymphs or immature forms, which are yellowish orange to green in color, and flat and elliptical in shape. The nymphs are somewhat similar to those of certain whiteflies, and are normally found on the under surface of the leaves. They have a row of wax glands. When abun- dant, the white wax which is secreted may be seen on the leaves and even on the ground about the plants. Nournishment is obtained by sucking up the cell sap. Injury is caused by a toxic substance which is injected into the plant. This causes a stunting of the plant and a yel- lowing and curling of the leaves; a con- dition known as "psyllid yellows." The tomato psyllid attacks a number of different plants and is at times a serious pest of tomato and potato. Damage by the pest in California is localized and is limited to the cooler coastal regions. Nymphs of the tomato psyllid are shown with white dots of excrement. CONTROL: The tomato psyllid can be controlled with either malathion, DDT, or sulfur compounds. Treatment is ap- plied at first evidence of infestation and should be repeated at 2-week intervals until the pest is thoroughly controlled. Follow directions on the label if mala- thion or DDT is used. Dusting sulfur thoroughly applied gives good control. If a spray is desired, use 1 heaping table- spoon of wettable sulfur, or a heaping tablespoon of dry lime-sulfur to a gallon of water. In order to insure successful control, the insecticides must be thor- oughly applied, so that the pests on the undersides of the leaves are contacted. TOMATO RUSSET MITE The tomato mite is free living and microscopic. Under a magnifying glass this extremely small mite appears pear- shaped and whitish yellow. It crawls about slowly on the surface of the stems and leaves of the tomato plant, sucking CONTACT INSECTICIDES FOR SUCKING PESTS [35] The lower leaves of this tomato plant are dry- ing and dropping after mite injury. the juices. These parts of the plant later appear oily brown or russeted. Starting on the stems near the ground, the in- festation works up the plants gradually, causing the lower leaves to dry and drop. In time the entire plant may be defoliated. This mite is among the most destructive tomato pests in California. CONTROL: The tomato mite is con- trolled by thoroughly and evenly treat- ing the plants with dusting sulfur before serious damage occurs. As a rule the vines should be dusted between June 1 and July 15, and thereafter every 2 to 4 weeks. If the plant is also infested with worms, a dust mixture of sulfur and cryolite, or sulfur and calcium arsenate, or sulfur and DDT, or sulfur and DDD may be used. If any one of these dust mixtures is applied during the harvest period, the tomatoes must be washed or thoroughly wiped or peeled before they are eaten. Sulfur, because of its action on metal cans and lids, has a harmful ef- fect upon tomatoes that are canned; this is why tomatoes must be free of it. Do not grow tomatoes near petunias, a favorite host of the mite. WHITEFLIES Whiteflies are sucking insects about Y 16 inch long. The body and wings of the adults are covered with a fine, whitish, powdery wax, from which the name is derived. Although the adults feed, it is the scalelike nymphs, or immature forms, which cause the damage. They suck the cell sap from the plant tissue. In heavy infestations the leaves turn yellow, finalh die, and drop. The nymphs secrete quan- tities of honeydew, which attracts ants, and on which a sooty mold fungus grows. Whiteflies infest many kinds of culti- vated plants and often occur in abun- dance on weeds, such as morning-glory. The nymphs are found on the under sur- face of the leaves. CONTROL: Whiteflies are controlled with contact insecticides. Malathion or malathion and oil sprays are effective. Oil-and-nicotine or oil-and-pyrethrum sprays are also effective. All of these are available as commercial preparations. Another spray — nicotine and soap — is effective. Since whiteflies occur mostly on the undersides of leaves, this under sur- face must be thoroughly wet with the spray. At least two and possibly three ap- plications at seven-day intervals are necessary to control this pest once an in- festation is established. Destroy infested plants as soon as harvest is complete. , - ; ,. V^ , ; *• ^v ■ «■■■■■■'.-■,'.,■ ■; : --; : : The nymphs of the whitefly feed on the under- side of leaves. f36] ROOT-KNOT NEMATODE* (Not an insect but has sucking habits.) The root-knot nematode, sometimes called "eelworm" or "garden nematode" is a microscopic worm which invades the roots of many garden plants and remains there as a parasite. It causes the forma- tion of galls on the roots of susceptible plants. These galls interrupt the flow of water so that heavily infected plants be- come unthrifty, have poor color, wilt, and sometimes die. These nematodes are widely distributed throughout California and are particularly destructive in the warmer regions. Root-knot nematodes are usually most destructive in sandy soils. They may be introduced into home gardens in infested seed potatoes, or on the roots of infected plants, or carried in with infested soil. Plants vary in their susceptibility to root-knot nematodes. Among the less-re- sistant hosts are such plants as beans, potatoes, tomatoes, melons, rose, snap- dragon, and pansy. Such plants as corn, onion, strawberry, gladiolus, nasturtium, iris, lily, tulip, and narcissus are rela- tively resistant to attack. When nematode injury is suspected, it can be determined by digging up the roots and examining them for galls. On most host plants the galls are conspicu- ous and occasionally grow to a diameter of an inch or more. Nematode galls must be distinguished from the beneficial nodules of the nitrogen-fixing bacteria which occur on leguminous plants. The latter are loosely attached to the sides of the roots, while nematode galls involve all root tissues and cannot be separated from them. CONTROL: Where serious infestations of root-knot nematodes occur, resistant varieties of plants can be used. Because warm weather is necessary for the nema- tode to be destructive, many susceptible plants can be grown in the winter at a time when the nematodes are least active. Chemical control of root-knot nema- todes in the home garden is possible. These treatments have certain limitations but if properly applied control can be successful. The most effective chemicals are soil fumigants containing dichloro- propene, ethylene dibromide, dibromo- chloropropane, chloropicrin, or sodium H-methyl dithiocarbamate. Some of these fumigants are packaged in containers for use in the home garden. Where fumigants are used, the infested soil should be in good tilth before application, and must be treated at least two weeks before the ground is planted. These chemicals, with the possible exception of dibromochloro- propane, should never be applied closer than within 30 inches of growing plants. Where trees and shrubs are growing, never treat within the drip area of such plants. The directions for the use of these fu- migants are given on the container and in instructions that can be obtained at the time the fumigants are purchased. For the best results, the dosage rates and procedures recommended on the con< tainer should be closely followed. * The authors are indebted to Merlin W. Allen, Professor of Plant Nematology and Plant Nematologist in the Experiment Station, Berke- ley, for assistance in the preparation of this section. Fumigants must be used with cau- tion. They are toxic to humans and animals. If spilled on the skin wash thoroughly with soap and water. Clothing that has become contami- nated should be thoroughly cleaned before being worn again. Avoid pro- longed breathing of the fumes of these nematocides. [37] The Diseases Ornamental and vegetable plants are subject to many diseases. Remedies for some of these are not known or are not practical for the home gardener to use. Frequently, symptoms of a disease be- come apparent too late for anything to be done on the crops concerned. However, as will be shown, various measures can be taken in the home garden to avoid or reduce the damage caused by many of the diseases that occur. The subject of dis- eases of plants is vast, and because of this, only a few of the more common diseases are included in this discussion. SOIL-BORNE DISEASES Many of the disease problems con- fronting the home gardener originate in the soil. These may result from organ- isms, such as fungi, that are natural in- habitants or have been introduced and become established there. Many of the disorders may be the result of poor cul- tural practices or the result of excesses or deficiencies of one or more mineral salts. DAMPING-OFF DISEASES Damping-off is a serious disease in seed and plant beds and may be caused by any one of several fungi. Two distinct types, preemergence and postemergence damping-off, are recognized. In pre- emergence damping-off, which is most serious in cold, wet soils, the sprouting seeds rot before they break through the surface of the soil. This results in bare spaces in the rows where the plants should be and is usually blamed on poor seed. Postemergence damping-off results in wilting or rotting of the seedlings after they emerge and is more common in warm, humid weather when the plants are grown in crowded conditions. Infected succulent plants wilt and topple over, whereas infected woody plants wilt but frequently remain upright. Root and crown decay may then follow. CONTROL: The best control for damp- ing-off is to prevent its start. This may be done by germinating seeds in pasteurized soil or in an inert medium such as sphagnum moss or vermiculite. Soil can be pasteurized by heat or by chemicals. Heat is the most effective means of treat- ing soil-borne pathogens in limited amounts of soil or in restricted areas. Heat may be applied in the wet form of steam or hot water, or in dry form as electricity or hot air. An important factor to remember is that soil should be uni- formly heated to 160° to 180° F for at least io hour. Soil pasteurized in this way can be used for planting as soon as it cools. For pasteurizing larger amounts of soil, or where heat is not practical, chemi- cal treatments may be used. Three of the commonest chemicals used are formalde- hyde, methyl bromide, and chloropicrin (tear gas). They all have certain disad- vantages — they are irritating or harmful to the person making the applications, the soil must be aerated following treatment, and they cannot be used around growing plants. However, these materials give very good control of the damping-off or- ganisms. Information about the use of chemicals to pasteurize soil can be ob- tained from the University of California Farm Advisor's office in your county. Recently, several new chemical prod- ucts have been released which are very [38] good for controlling damping-off organ- isms. One of these, known as Panogen, when mixed 1 : 10,000 and sprinkled over the soil just prior to seeding, protects the developing seedlings. A second com- pound. Anti-damp, is reported to give good control when diluted 1:100 and applied to the soil. Both compounds can be watered into the soil right after seeds are sown and since they are not injurious to growing plants when used at the recommended dilutions, the treatment can be repeated if trouble should develop as the young plants emerge. Another means of controlling damp- ing-off is by the use of seed protectant fungicides. These chemicals, when ap- plied to the seed, disinfect the soil im- mediately around the seed and give tem- porary protection while the plant is in a very susceptible stage. Many good seed protectants are on the market, among which are Ceresan, Semesan, Cuprocide, Arasan, Tersan, Fermate, Spergon, Phy- gon, and Dow compounds 6, 9, and 10. Most of these are very good. Some, how- ever, are better for certain seeds than others. These should be applied accord- ing to the recommendations of the manu- facturer. Certain of these chemicals can be mixed with the soil to control damp- ing-off. For instance, one teaspoon of Arasan mixed in a flat of soil protects certain seedlings from damping-off or- ganisms. Small experiments with differ- ent materials and different plants mav give desirable results. Captan has also given good control when mixed in the soil. WATER MOLD ROOT ROT Water mold root rot is caused by some of the fungi that are closely related to several of the damping-off organisms, and may cause serious damage under condi- tions of excess soil moisture. This disease is of frequent occurrence in heavy soil with poor drainage. A number of plants are attacked, the more common being azaleas, rhododendrons, camellias, heath- ers, and many of the ornamental conifers. Young plants are usually attacked but it is not uncommon to see older plants die from this trouble. Infected plants show an unthrifty appearance. This may be followed by permanent wilting, leaf-drop, and eventually death of the plant. The portion of the main stem at and below the soil line becomes brown; a cut into this area reveals only dead bark and wood. CONTROL: The control is a matter of prevention, since a well-drained, aerated soil will prevent development of the disease. ARMILLARIA ROOT ROT The fungus causing Armillaria root rot is widespread in California. The disease is also known as oak root fungus disease, shoestring root rot, mushroom or toad- stool root rot, or oak root rot. The fungus is known to attack at least 470 species of plants. It usually attacks conifers, de- ciduous trees and broadleaf evergreens, but may also attack herbaceous plants. All plants are not equally susceptible to the fungus and some trees may be in- fected with no apparent damage. The external symptoms are not always diagnostic. The infected plants may ap- pear unthrifty and may either linger on for a long time or die suddenly. The most reliable sign of the disease is the pres- ence of large white mycelial fans or plaques found between the bark and wood of the roots and crowns of the infected plants (see page 40) . In advanced stages, the wood becomes wet and soggy. At certain times of the year the fungus mav produce mushrooms at the crown of the infected plants (see page 40) . This mush- room gives the disease its name "mush- room root rot" or "toadstool root rot." CONTROL: Control of this disease is very difficult. Soil fumigation is one method that has proved effective in many areas. The best chemical at present is carbon bisulfide. It is injected 6 or 7 [39] Left. Large white mycelial fans or plaques between bark and wood of roots and crowns of infected plants are the most reliable signs of Armillaria root rot. Right. Fruiting bodies or mush- rooms of the oak root fungus arising from an infected plant. inches deep into the soil at the rate of 2 ounces (59 ml) every 18 inches. The starting point of each injection row is staggered to provide better coverage. Most of the roots of infected plants should be removed before injecting the chemical. The use of carbon bisulfide presents several difficulties in the home garden. The chemical kills all plants in the treated area and since roots of in- fected plants may extend for quite a dis- tance in the soil, large areas of the garden may be involved. Fumigation with the chemical is more effective if the soil is dry. This is difficult in a garden where water is needed to keep some of the de- sired plants alive. Exposing the crowns of infected plants may prolong their lives because the fungus is not favored by dry conditions. Improving drainage in the soil also helps to control the disease, especially in those plants which show some resistance to the fungus. The home gardener's best control is to plant resistant species of trees and shrubs. The University has a list of ornamental plants, available on request, that have been tested and found to have some re- sistance to the disease. VERTICILLIUM WILT Verticillium wilt is another very wide- spread disease in California. If the fungus that causes this disease is once estab- lished in soil favorable to its develop- ment it will remain for long periods, and any susceptible plants placed in the in- fested soil may be subject to attack. The disease can be recognized by the yellowing of the lower leaves followed by death of the marginal tissues and, even- tually, death and sometimes defoliation of the lower plant. Examination of a cut section of the stem will usually reveal a brown discoloration in the woody part. The fungus has a wide host range; in fact, a list of susceptible plants is too long to give here. It is particularly bad in tomatoes, potatoes, strawberries, and various melons. Other plants that are quite susceptible are chrysanthemum, rose, China aster, marguerite, eggplant. New Zealand spinach, dahlias, peonies, snapdragon, Salpiglossis, strawflower, maple, elm. and many trailing berries. CONTROL: Control of this disease is difficult but a number of methods should prove helpful to the home gardener. If potatoes or tomatoes are grown, they [40] should not be followed with a susceptible crop, but with one which is resistant, such as beans, beets, spinach, corn, or flowers such as petunias, pinks, marigold, calendulas, sweet pea, delphinium, be- gonias, or flowering bulbs. Resistant varieties, where available, should be grown. Some varieties of chrys- anthemum are quite tolerant of the fun- gus. Manetti rose, used as rootstock, is very resistant, and some of the flowering varieties of roses show more resistance than do others. Another good control method is fumi- gation of the soil with chloropicrin. This may be done with a hand applicator or even a syringe and a hypodermic needle. For best results, soil should be slightly moist and fairly warm. About % tea- spoon (3 milliliters) of the chemical is injected 6 inches deep at 1-foot intervals. The beginning of the rows is staggered to give better coverage. As soon as the chemical has been injected, the hole should be tamped shut. When the injec- tions are completed, a light sprinkling of water over the surface of the soil to moisten the surface layer is helpful. It is necessary to wait about two weeks before planting in an area treated in this way. SALT DAMAGE A disorder of many plants, the symp- tons resembling somewhat those of Ver- ticillium wilt, results from too high a salt concentration in the soil and in the water. The injury, which is quite common in California, appears on the aerial portions of the plant as a marginal burning of the leaves (see opposite). Many plants are affected but salt injury is especially common on rhododendrons, azaleas, ca- mellias, gardenias, and magnolias. An occasional heavy watering to leach the excess salt from the soil is the best con- trol. If the plant is in a container, soak- ing the container overnight in a tub of water will help to leach the salts. Im- proving drainage will also help to control Salt damage on magnolia leaf. The injury usually appears as a marginal burning of older leaves. the difficulty. If this problem is serious, using organic fertilizers such as hoof and horn, blood meal, fish emulsion, et cetera, in place of inorganic fertilizers will help. When using any fertilizer, follow direc- tions on the container. MINERAL DEFICIENCY DISEASES In addition to the diseases resulting from mineral excesses, there are also dis- eases resulting from mineral deficiencies. Many of the conditions can be corrected by the addition to the soil of the lacking element. The lime concentration of the soil in many areas of California makes certain elements such as zinc, manganese, and iron unavailable to the plant. Iron deficiency is the commonest. The most striking symptom of this disorder is a yellowing or chlorosis of the younger leaves (see page 42). The yellowing begins at the outer margins and pro- gresses inward, the veins being the last to lose their green color. Ornamental plants commonly affected are acacia, abelia. magnolia, gardenia, hydrangea. r 4i i Iron chlorosis of hydrangea. Leaves showing advancing stages of this disorder, which begins as a yellowing at the outer margins and progresses inward, the veins being the last to lose color. azalea, rhododendron, and liquidambar. Peach and pear are also affected. CONTROL: The best control is to make the soil more acid. This can be done by adding sulfur, or by incorporating or- ganic matter into the soil. Spraying the foliage with iron sulfate will frequently give control, but it is not permanent and must be repeated. Another material that has given very good results when sprayed or applied to the soil on some plants is a material sold under the trade name Greenz-26. This material, which contains iron, when mixed with water at the rate of 4 ounces to 5 gallons may be sprayed on the foliage to correct the deficiency. Certain plants may not respond to a foliage application of this material but may show response when the material is added to the irrigation water at the rate of 8 ounces per 5 gallons. Iron seques- trene is another material which can be sprayed on the growing plants or added to the soil. With this material, it is ex- tremely important to carefully follow the manufacturer's directions or plant injury may result. STEM, FOLIAGE, AND FLOWER DISEASES (Powdery mildew) The powdery mildews are the com- monest and the most troublesome of the foliage diseases in California. These dis- eases are caused by several closely related fungus forms that attack a large number of host plants. They are especially serious on roses, dahlias, tuberous begonias, zinnias, calendulas, sweet peas, phlox, Left. Powdery mildew of euonymus showing typical powdery growth of causal fungus. Right. Sunburn of rhododendron. Three leaves show characteristic brown area through the center of the leaves. Leaf on right shows the brown area after it has been invaded by secondary fungi. [42] live oak, euonymus, flowering crabs, peaches, apples, grapes, beans, and cu- curbit species such as squash, canta- loupes, cucumbers, et cetera. The fungus grows entirely on the sur- face of the leaves, obtaining its food by sending minute pegs into the cells of the leaf. The masses of white fungus body and the spore-bearing branches which appear on the surface of the leaf have re- sulted in the name "powdery mildew." Most fungi require free water before the spores can germinate and cause infection, but the powdery mildew spores are unique in that they can germinate and cause infection in the absence of free moisture. For this reason, these diseases are very serious, even during dry periods and, also, because of this, are difficult to control. CONTROL: Two chemicals can be used to control powdery mildews. Dusting sul- fur is an old but still very effective means of controlling these fungi. In addition, a new material known as Karathane (also available as Mildex) has been found to give excellent control on many crops in- cluding roses, begonias, chrysanthe- mums, zinnias, and dahlias. Care must be taken in using these materials, especially . Rust on snapdragon. The casual fungi pro- duce small pustules which rupture and release red, brown or yellow spores. These give the in- fected leaves a rusty appearance. during hot weather, since they can cause considerable foliage damage if used on plants sensitive to them. It is suggested that the tolerance of a particular plant be determined before using these chemi- cals extensively. SUNBURN Some of the shade-loving plants, such as rhododendron, camellia, and azalea, occasionally will be burned by too much sun. This injury appears as a large brown area down the center of the leaves (see page 42) . Not only is it unsightly, but it allows the entrance of organisms that would not be able to enter healthy tissue; in turn, these organisms make the injury more unsightly. CONTROL: The control is to place susceptible plants in desirable locations; once they are established and doing well, do not move them to sunnier locations. RUST DISEASES Diseases known as the rusts are quite prevalent in many areas of California. They are so named because on infected surfaces the causal fungi produce small pustules which rupture, releasing red, brown, or yellow spores that give the plant a rusty appearance (see opposite). The most commonly affected garden plants are rose, chrysanthemum, snap- dragon, carnation, hollyhock, iris, and heuchera. Merion and Kentucky bluegrass are also attacked by rust fungi. The disease first appears as reddish brown and orange patches that usually spread rapidly until the entire lawn may be affected. Growth of the grass is then much reduced. CONTROL: Control rust fungi by spraying with zineb (commonly sold un- der the trade names Parzate and Di- thane Z-78). In addition, certain cultural practices will help in the control of these diseases. Raking up and burning leaves from the infected plant help remove the [43] overwintering stages of the fungi. With roses, pruning back so that no foliage is left on the plant helps to keep the disease from carrying over from one season to the next. Watering plants in the morning or watering so that none is splashed on the foliage helps to control some of the rust diseases. Control of the disease in Merion and Kentucky bluegrasses is difficult. Acti- dione, a new antibiotic, and actidione, ferrated, are reported to give fair control of stem rust when used as a foliage spray. Actidione is sold in tablet form and the spray is prepared by dissolving 1 tablet (380 mg) in 1 gallon of water. A wetting agent such as a kitchen detergent should be added to insure good coverage. Keep- ing the lawn well fertilized and mowed high will help reduce the damage caused by this disease. TWIG DIEBACK OF ROSE Twig dieback of rose is a common disease caused by a fungus considered to be a weak invader. It usually enters through pruning wounds and kills the stump above the bud, but may occasion- ally invade beyond and kill the whole branch. CONTROL: The control is simple and consists of pruning just above a bud so that there is no stub or "dead end" wood. ANTHRACNOSE OF SYCAMORE This disease is very common in syca- more trees in California. It is caused by a fungus which attacks only the develop- ing leaves and twigs causing the leaves to turn brown and die (see page 45). De- foliation usually results from these infec- tions. CONTROL: The best control measure is to spray the trees with a protective fungicide. Time of spray application is important. Spraying with Vancide 51 or zineb (sold as Dithane Z-78 or Parzate) in two applications as a delayed dormant and broken bud stage or as broken bud and young leaf stage will give good con- trol. It is also helpful to prune out in- fected twigs and branches. SCORCH OF MODESTO ASH This disease is similar to sycamore anthracnose but differs in that the leaves of the ash tree are susceptible at all stages of development. The fungus causing this disease attacks the leaves during wet weather, causing brown patches over large areas and at the edges (see page 45). It may also cause some defoliation. CONTROL: Control of the disease is by protective fungicides. The same fun- gicides used to control sycamore an- thracnose will probably be effective against scorch. Since the disease is spread entirely by rainfall, a good coverage on the young leaves during the rainy season is important. FIRE BLIGHT Fire blight is a disease resulting from a bacterial infection. The bacteria enter the plant primarily through flowers but also through natural openings or wounds. The disease causes serious damage on pears and apples. It may also affect such ornamental plants as flowering crabs, pyraeantha, and hawthorn. The disease is recognized by a sudden wilting of in- fected blossoms, which, after a short time, turn brown (see page 45). Leaves and twigs may also be killed. The dead leaves cling to the twigs and the aifected branches appear to have been scorched by fire — hence the name "fire blight." CONTROL: The disease can be con- trolled by the application of fixed copper (about 1 teaspoon per gallon of water) as a spray during the blossoming period. If the plants continue to bloom for some time, two or three applications at 5-day intervals may be necessary. About */2 teaspoon of Dreft or other kitchen deter- gent added to the copper and water mix- ture will insure better coverage by the spray material. Pruning out infected [44] / € Sycamore anthracnose attacks only the de- veloping leaves and twigs and causes much leaf drop. The leaf tissues around the veins are most frequently attacked. Scorch of Modesto ash. The fungus causing this disease attacks the new foliage during wet weather, resulting in scattered, brown patches of dead leaf tissue throughout the leaves. wood and twigs 6 to 8 inches below the diseased area should also be done to in- sure good control. This removes the prin- cipal source of inoculum. The pruning shears should be sterilized between each cut with a Lysol solution (1 part of Lysol diluted with 9 parts of water). Pruning alone may be all that is necessary for Fire blight of pear may be recognized by a sudden wilting of infected blossoms which, after a short time, turn brown. control if the affected plant is well iso- lated from other susceptible plants. PEACH LEAF CURL This is a disease principally affecting peach. It is caused by a fungus that sur- vives unfavorable conditions as spores lodged on the surface of the tree. When Peach leaf curl causes the young developing leaves to thicken and curl. The parts affected may vary in color from buff to bright red. [45] conditions are suitable in the spring, the spores germinate and infect the young developing leaves, causing them to thicken and curl (see page 45). The af- fected parts may vary in color from buff to bright red. Infected leaves usually wither and drop off. The infection may be serious enough to cause much defoliation. CONTROL: The disease can be easily controlled by applying a spray before the buds begin to swell in the spring. Ferbam, or Ziram. or a fixed copper fungicide have all proved to give ade- quate protection for this disease. IRIS LEAF SPOT A disease common on iris in California is one caused by a fungus and known as leaf spot. The first evidence of the trouble is the appearance on the leaves of small brown spots surrounded by a water- soaked margin. The spots enlarge until Iris leaf spot. Infected areas appear as round spots. These may enlarge, coalesce, and sometimes cause premature death of the entire leaf. they coalesce. Parts of the infected leaves, particularly toward the tip, die, and sometimes the whole leaf may die pre- maturely (see opposite). The centers of the older spots become gray with a red- dish-brown border. CONTROL: The fungus overwinters in the old leaves and the best method of re- ducing this disease is to carefully remove and burn all of the leaves in the autumn months. Spraying with the fungicide Fer- mate, applied when the leaves are de- veloping, will help protect the leaves against infection. The heavy, waxy coat- ing on the leaves of iris makes it very difficult to get good coverage with fungi- cides and therefore the addition of a spreader-sticker is necessary. VIRUS DISEASES Many of the diseases encountered in the home garden are the result of virus in- fections. Viruses are extremely small en- tities that are spread in various ways. They are transmitted, most commonly, by certain insects. This is done when the in- sect, after feeding on a diseased plant, moves to a healthy plant and injects the virus it carries into the plant during the feeding process. Another means by which viruses may be transmitted is by contact between diseased and healthy plants, or by implements contacting first a diseased plant and then a healthy plant. Certain viruses may be carried within the seed but this method of transmission is not common. Plants propagated by vegeta- tive means form still another means of spreading viruses. Cuttings, scions, tu- bers, bulbs, et cetera taken from a virus- diseased mother plant almost invariably harbor the virus. Symptoms expressed by virus-infected plants are variable. Usually, infected plants are stunted and appear unthrifty. Commonly, the first evidence of the dis- ease is seen on the leaves. It may appear as a mottle which has given rise to the term "mosaic disease" (see specimens [46 If "J&SXZ Carina mosaic and rose mosaic. The first evidence of virus-infected plants may be a mottle or a yellowing of tissues, which has given rise to the term "mosaic disease." here), or may be a general yellowing of the foliage that is frequently confused with deficiency diseases. Many viruses cause distortion of the leaves and stems. Color "breaking" in many flowers is the result of a virus infection. CONTROL: Control of virus diseases is difficult, and once a plant is infected nothing can be done for that particular plant. Removing and destroying infected plants will serve to minimize the danger of spread. Control of insect vectors, al- though not very successful over large areas, may be helpful in preventing spread of the virus in the home garden. Since virus diseases can become, and fre- quently are, very serious in vegetatively propagated plants, care should be taken to select only those plants for propagation that are free of virus. In our publications it is sometimes convenient to use trade names of products or equipment rather than scientific identifications. In so doing it is unavoidable in some cases that similar products which are on the market under other trade names may not be cited. No endorsement of named products is intended nor is criticism implied of similar products which are not mentioned. Co-operarive Ext co-operating. Di: ision work in Agriculture and Home Economics, College of Agr ibuted in furtherance of the Acts of Congress of May 8, and Jun ulture. University of California, and United States Department of Agriculture 30, 1914. George B. Alcorn, Director, California Agricultural Extension Service. 40wi-6,'59(C6937)MH PURPOSES OF A UNIVERSITY. ..to explore see new visi .find new riches "I like to compare scientific research to mountain climbing in an unexplored range. Considerable preparation, training, and a strong motivation are required to get up to the upper altitudes even if no one particular stretch of the way is particularly difficult. But once there, it is relatively easy for one to see vistas or even to stumble across new riches that people of equivalent ability who have stayed behind, have no possibility to see or to find." Glenn T. Seaborg Chancellor at Berkeley Nobel Laureate in Chemistry, 1951 (From his address at the Secondary Education Board Conference. San Francisco. April 5, J957)