PK Division of Agricultural Sciences UNIVERSITY OF CALIFORNIA Vr^^Q INSECT and MITE PESTS of ALMONDS FRANCIS M. SUMMERS CALIFORNIA AGRICULTURAL Experiment Station Extension Service CIRCULAR 513 INSECT and MITE Almond growers must be able to detect signs of a pest infestation early to prevent its spread. This publication tells how to recognize major insect and mite pests and describes their life histories. Almond pesticides, as well as the problem of preventing hull contamination, are discussed but no specific spraying programs are given. For information about moths, see page 3. mites, see page 10. plant bugs, see page 12. scales, see page 13. beetles, see page 15. pesticides, see page 15. THE AUTHOR: Francis M. Summers is Professor of Entomology and Entomologist in the Experiment Station, Davis. JUNE, 1962 A t least thirty distinct species of in- jurious insects and mites attack Califor- nia's almond orchards. Some are widely distributed, while others invade very lim- ited areas. The pests are not specifically restricted to almond, hut may infest other fruit trees, especially peach. The almond is, however, a preferred host for several pests, particularly the peach twig borer and the brown mite. Pesticides which are safe for use on stone fruit trees must be used much more cautiously on almond trees to prevent contamination of forage hulls. Almond insect and mite pests can be grouped into five categories: moths, mites, plant bugs, scales, and wood-boring beetles. Of these, the moths are perhaps the greatest economic menace to almond growers. PESTS of ALMONDS Moths mportant moth pests . . . type and extent of damage . . . habits . . . use of pesticides PEACH TWIG BORER The peach twig borer, Anarsia linea- tella Zell., is one of the most damaging pests of almonds. From 1933 to 1952 the total yearly damage to Nonpareil meats delivered to the California Almond Grow- ers Exchange ranged from 1.00 to 8.34 per cent by weight. The larvae feed mainly on the hull or outer shell tissues and rarely attack the meats of hardshell varieties. However, when heavy infesta- tions develop, some of the larvae enter the nuts and damage the meats of soft- shell varieties. The surfaces of ripening meats are usually scored or etched away with shallow channels or, occasionally, small bits are chewed away from the pointed ends. Actively feeding larvae (worms) are rarely found in dry nuts on trees or in stored nuts or meats. The larva of the peach twig borer can be recognized by its body color and twig- mining habit. A mature larva is about % inch long. It has a black head and a red- brown or chocolate-colored body. The soft membranes which join the body seg- ments together are pale brown, so that wide bands of darker color alternate with narrow bands of lighter color. The adult stage of the twig borer is a small slate- colored moth. During daylight hours it rests on shaded trunks and main limbs of host trees. The moths are so well camou- flaged that they are very difficult to find unless the rough bark and bark crevices are intently searched. Habits. The larvae of the twig borer feed primarily within the tender twigs of stone fruit and almond trees. A larva just out of the egg stage usually bores into the petiole of an immature leaf near a ter- minal bud, and then moves downward 2 or 3 inches through the core of the shoot. Since mined twigs die back, the number of twig borers is roughly indicated by the number of dead terminals showing after a brood of larvae has matured. Very young larvae winter under the [3 #te». Infested twig split open to show burrow and mature larva of the peach twig borer. Below. Terminal shoot killed by a peach twig borer. soft bark of young wood. Many of those which hatch from eggs laid during the latter part of the growing season chew directly into the tender hark or callous tissue in the crotches of small branches where they construct cavities called hiber- nacula. They become quiescent when es- tablished, and overwinter as very small, immature worms. Apparently, the whole orchard population of twig borers is con- fined on the exposed wood of fruit and nut trees between growing seasons. Win- ter sprays which kill the hidden lar- vae are therefore of strategic value. Dormant sprays containing spray oil plus certain organophosphate insecticides are effective against the hibernating larvae. The small larvae emerge from their hibernacula during the blooming period, the first few coming out during late Jan- uary. Emergence builds to a peak during the first half of March and then declines, but diminishing numbers of stragglers may appear until mid-April. Thus the new season of twig borer attack begins with a brood of larvae generated the sea- son before. Since foliage is undeveloped at the time " [4 of peak emergence, larvae bore into un- opened fruit and shoot buds; later, they establish themselves in larger shoots to finish the feeding stage. Excellent con- trol can be accomplished by spray- ing to destroy emerging larvae of this brood during pink bud or immediately after petal fall. Chemi- cals which control twig borers should not be used during the blooming period be- cause they are harmful to pollinators. All larvae of the overwintered brood mature and move out of the foliage dur- ing April. This phase ends about May 1 ; during April and May the larvae spin cocoons on the tree trunks and transform into moths. Eggs laid by these moths begin to hatch between May 10 and May 20, and this new brood mines twigs dur- ing late May and all of June. Sprays applied at the onset of this attack are known to give excellent results but pesti- cides used at this period can cause illegal contamination of forage hulls. Present and future pesticides acceptable for use during this first multiplication period must be applied with full understanding of the prevailing residue restrictions. A third brood begins to appear during early July. Larvae of this and possibly a fourth brood appear almost continuously throughout the crop-ripening period and some of them feed on maturing nuts. Controlling these later broods is very difficult and cannot be assured. NAVEL ORANGEWORM The navel orangeworm, Paramyelois transitella (Walk.), is a moth pest which first appeared in Mexico and Arizona as a scavenger of citrus fruits. Within the past fifteen years it has become wide- Chimney of silk and frass in twig crotch marks location of a live peach twig borer larva in its hibernaculum. spread throughout the almond and wal- nut growing areas of California. It can survive and propagate in nut and fruit orchards when suitable food is available. Apparently within several seasons after infestation, the pest builds up to a notice- able economic level. It then regresses to a low-grade chronic infestation which causes only minor loss but still presents the threat of serious outbreak. The navel orangeworm moth is small (wingspread is approximately % inch) and pale gray with brown and black markings. The mature larva, or worm stage, is about % inch long and is cream, flesh or pale pink except for its dark- brown head. A tiny inverted crescent or horseshoe of dark skeleton is located high on each side of the second body segment behind the head; this partly surrounds two bristles and is hardly visible except with a pocket magnifier. Larvae are apt to be present when recently harvested New information and regulations about almond pesticides are constantly being developed. Growers interested in obtaining information on specific pesticides and conditions of use should secure the current University of California pest control recommendations from their Farm Advisors or from the Public Service Office. [5] Above. Larva of navel orangeworm in a Nonpareil almond. Left. A navel orangeworm moth. almonds are opened. Older larvae may be identified by their method of feeding on almond meats. They devour substantial amounts of kernel, forming cavities or tunnels which are partly filled with frass (excrement pellets) and dirty web. Habits. The habits of the adult or moth stage are not well known, but pre- sumably adults do not survive the winter. Eggs laid when the growing season is about to end produce larvae which over- winter within mummy fruits or un- harvested nuts. The nuts may be stick- tights or good nuts left hanging or lodged in crotches of the trees. Larvae in young or advanced stages of growth, and even pupae or chrysalids, often occur together within one fruit or nut. The navel orange- worm does not appear to have a true quiescent or hibernating stage. Low tem- peratures merely slow growth and feeding processes. Since the larvae do not feed on whole, green almonds, the population is perpetu- ated on holdover nuts during much of each year. Moths active in spring months lay eggs on year-old nuts, some of which already contain larvae of an earlier gen- eration. Reproduction continues through- out the growing season; there are no clear-cut worm broods or intermittent moth flights. Since orangeworms do not bore through almond hulls, the larvae infest nuts of the new crop when the hulls begin to crack in the preharvest period. A few larvae mature and produce moths before harvest but most remain in the nuts until Pupa of navel orangeworm in a mummy almond during spring. Kernel is entirely consumed. the crop is harvested and are carried over into the storage period. Maturation time in stored nuts varies according to the age of the larvae on harvest date and accord- ing to temperature. Low temperatures greatly prolong the time required to com- plete growth. This pest is also a processor's problem because live worms continue to damage nuts in receiving depots and storage bins. Orangeworms are "dirty feeders"; as meats are partly devoured, coarse frass and profuse webbing appear on them. A full-grown larva generally leaves the infested nut in search of a place to spin its cocoon, and as it moves about it produces copious amounts of dirty web which binds nuts together and contami- nates sacks or bins. Processors can lessen this problem by fumigating all infested lots immediately on arrival. This sanita- tion procedure benefits the producer, be- cause larvae which are very small at the time of fumigation are destroyed before they can do enough damage to make meats unsalable. No practical spray procedure has been devised to control the navel orangeworm. Test sprays of the best in- secticides now known (applied in one or two sprays after hull-crack) have not significantly reduced crop damage. On the other hand, research has shown that sound crop management can reduce crop losses. These four pro- cedures have proved profitable: 1) Har- vest trees as completely as economics per- mits, removing unharvested crops from diseased or neglected trees. 2) Harvest susceptible varieties (IXL, NePlus, Non- pareil, Drake) as early as harvesting methods and good quality permit. 3) Route susceptible varieties through the huller first; unhatched eggs on fresh hulls are a threat to meats until hulls and nuts are separated. 4) Ship lots to the processor immediately for fumigation, if the service is available. Almonds picked in mid-April to show damage caused by larvae of fruit-tree leaf roller. [7] Mature larva of a tent caterpillar. OTHER MOTH PESTS Although twig borers and navel orangeworms are the major moth pests which attack near-ripe almonds, others which cause only minor losses complicate worm identification. The fruit-tree leaf roller, Archips argyrospilus (Walk.), attacks almonds in the late jacket period. The moth has a wide host range but is perhaps best known as a spring pest of apricots. The eggs, laid on small branches in button- like masses, begin to hatch during March or April. The larvae chew on leaves and tie them in rolls with tough strands of web; they also enter young almond fruits and devour the kernel. Crop damage, which is completed by the end of May, can readily be identified: dry, collapsed nuts of about one-third final size have fairly large slotlike holes into the kernel chamber but no kernels; often traces of web and a rim of frass surround the hole. Leaf roller infestations are local, spo- radic, and usually minor. A petal fall spray gives effective control. California tent caterpillars, Mala- cosoma calif ornicwn (Pack.), are large, gray or brown hairy larvae with a line of blue along each side. They are leaf feeders, appearing in spring in a few lo- calities. Tiny larvae hatch from masses of eggs affixed to the tree bark and soon spin sheets of web enmeshing one or more small shoots per tree. Later the large, mature caterpillars disperse to wander about on limbs and foliage be- fore transforming into moths. Satisfac- tory control can be obtained with residual insecticides applied during the petal fall period or shortly afterwards. The western peach tree borer, Sanninoidea exitiosa graefi (Hy. Edw.). sometimes infests almond trees in coun- ties near the San Francisco Bay area. This moth is a wood borer; its larvae are considerably larger than those of the prevalent fruitworms. They attack tree trunks close to the ground line (frass and plentiful gumming are revealing symp- toms) seriously damaging the tree if the larvae are numerous or if the attack con- [8] tinues for several seasons. The moths and eggs appear from late April through September, with a peak emergence close to August 1. Persistent pesticides, applied as trunk sprays at bimonthly intervals from May 15 through August, have been successful. Trunk sprays must be con- fined to the required part of the trees and not allowed to splatter onto fruit or foliage. The American plum borer, Euzo- phera scmijuneralis (Walk.), is one of several species of moth larvae sometimes found in the gummy, callous tissues of crown galls. This insect sometimes be- comes troublesome on new grafts. Scar tissue or callus formed at the union of scion and stock attracts this borer, and it works to undercut or girdle the graft. Brownish frass, web, and gum pockets indicate its presence. Excess grafting wax and detritus should be brushed away and the affected parts sprayed with DDT. Unharmed grafts should also be treated. Although standard procedures to control the pest have not been evolved, it is be- lieved that several applications of DDT are required to extend protection until scion-stock unions heal and harden. The codling moth, Carpocapsa pomonella (Linn.), a major pest of ap- ples, pears, and walnuts, occasionally at- tacks almonds, but infestations so far identified have been isolated and trivial. The raisin moth, Ephestia figulilella Greg., infests almond kernels during the harvest period but is not a significant orchard problem. This species and its close relative, the almond moth, can be troublesome storage pests, however. An- other fruitworm is the filbertworm, Melis- sopus latiferreanus (Wlsm.), which Work of western peach tree borer beneath heavy bark near ground line. breeds on oak galls and occasionally causes trouble in a few localities as an almond pest. No sprays are recommended, but the crop management procedures rec- ommended for navel orangeworm can minimize damage. An important and common storage pest is the Indian-meal moth, Plodia inter- punctella (Hbn.). Although it infests al- monds on trees, it is of no great conse- quence unless neglected when nuts are stored for long periods. New information and regulations about almond pesticides are constantly being developed. Growers interested in obtaining information on specific pesticides and conditions of use should secure the current University of California pest control recommendations from their Farm Advisors or from the Public Service Office. [9 Mites Important mite pests . . . how to recognize them . . . habits and methods of attack Many species of mites occur in almond orchards. Some are harmless inhabitants of topsoil, moss, lichens and moist tree bark; others are known to be predaceous and probably beneficial. Only harmful species will be discussed here. BROWN MITE The brown mite, Bryobia arborea ( M. and A.) , is the first spider mite to ap- pear in spring. It resides on the woody parts of the tree, feeding on the upper sides of almond leaves when conditions are favorable. This mite winters in the Almond leaf badly damaged by brown mite on the right. Leaf at left is bright green and free of mite damage. egg stage. Eggs are cemented to the sur- faces and in the crevices of wrinkled bark, sometimes in such large numbers that patches of wood have a reddish tinge. The eggs are spherical, cherry red, and have no filamentous attachments; freshly hatched mites are very small, fiery red, and have but six legs. The mites wander on foliage, distribut- ing their feeding punctures widely over leaf surfaces. Day-to-day changes in leaf symptoms are therefore difficult to de- tect. Affected leaves first become mottled, then decidedly yellow. Badly damaged fo- liage is bleached and covered with minute flecks of dried sap. Defoliation, however, is not a characteristic symptom of brown mite damage. Habits. Hatching of brown mites be- gins in late February and proceeds rap- idly throughout the blooming season. The so-called larval stage is succeeded by two nymphal growth stages before adults are formed — usually not before April 1. A multiplication period follows during April, when eggs are laid in large num- bers before the adults die. A second gen- eration of mites develops in May, and a third generation in June. Infestations re- cede during hot July weather, because most of the eggs laid during this period do not hatch. These eggs remain inert throughout the summer and the ensuing winter. Egg masses can be destroyed by dor- mant sprays containing oil and a suitable organophosphate insecticide or by spe- cific mite ovicides applied just prior to bloom. Control of actively feeding mites at petal fall or later is best ac- complished with persistent spray materials, lethal to both the active mites and their developing eggs. 10] EUROPEAN RED MITE The European red mite, Panonychus ulmi (K.), is a common spider mite pest of apple, pear, plum and, in some areas, peach. Although a serious fruit tree pest, it is not yet prevalent on almond. How- ever, it appears to be adapting to almond, since economic infestations are being re- ported with increasing frequency. Be- cause European red mite has quickly ac- quired resistance to a wide range of today's chemicals, it is difficult to con- trol. The pest winters in the egg stage as does the brown mite. The eggs are amber red and slightly flattened, often with a small filament projecting from the cen- ter of their exposed surfaces. The active, mature females are wine-red, with promi- nent back bristles projecting from white tubercles. These mites do not congregate in well- defined colonies on leaves. They are apt to be more difficult to control than brown mites because they continue to work well into late summer and may breed long after spring sprays have lost effective- ness. Symptoms of their feeding closely resemble brown mite damage, and al- mond growers who experience chronic troubles with "brown mites" should make certain that the offender is actually not the European red mite. PACIFIC SPIDER MITE The Pacific spider mite, Tetranychus pacificus McG., sometimes locally called "red spider," attacks the almond in sum- mer. It is green to yellow amber in the active stages, while the eggs are colorless spheres. A closely related species is the two-spotted spider mite, Tetranychus telarius (Linn.). Although properly dis- tinct species, the Pacific and two-spotted spider mites are so much alike in time and mode of attack, symptoms produced, and responses to chemical sprays, that the distinctions are not of consequence in practical control. Both frequently in- termingle on one tree and, occasionally, on a single leaf. The Pacific spider mite is web- spinning, forming colonies on both up- per and lower leaf surfaces. The leaf dam- age is localized; compact colonies pro- duce a slight cupping effect in the leaf and a local area of chlorosis (yellowing) or scorch. The species rarely attacks be- fore the advent of summer, but signifi- cant numbers appear quickly after warm weather begins in June or July. Trees already partly damaged by brown mites are likely to shed leaves sooner than those not damaged beforehand. Attack by Pacific spider mite characteristically begins in the driest and dustiest portions of orchards, then becomes general unless cool weather intervenes. Nonirrigated or- chards are most susceptible; sprinkler irrigated orchards appear to be least vul- nerable. If this species attacks severely before nuts complete development, counter measures are imperative to pre- vent sticktights and pinched kernels. Control of Pacific and two-spotted spider mites with modern miticides is quick and effective. One application of a residual miticide normally holds the in- festation in sufficient check; biological control usually takes over when chemical control lapses and the mites are unable to rebuild damaging populations before the onset of cool weather. Premature ap- plication of spray or incomplete cover- age, as well as protracted periods of high temperatures, increase the likelihood of a recurrent attack, however. The silver mite of peach, Aculus cornutus (Banks), also attacks almond trees. These mites, which are a species of leaf gall mites, are extremely small, flesh- colored leaf feeders, which stipple other- wise healthy green leaves with pin-point chlorotic spots. The symptoms resemble thrip or leafhopper damage. At present this species is not economically important in almond culture. [ii Plant Bugs Identification of the most damaging species . . . type of damage . . . two less important species BOXELDER BUG The boxelder bug, Leptocoris trivit- tatus (Say), affects bottomland orchards, especially in districts where boxelder, oak and elderberry abound. Adults are approximately % inch long, slender, and gray-brown to black. The orange-red color of the body beneath the wings is noticeable when the bugs are in flight. Boxelder bugs overwinter as adults which invade almond orchards very soon after blossoms fade. This migrant population is primarily responsible for crop damage. The pests can breed in orchards, deposit- ing eggs which are an aid to identifica- tion. These are laid singly or in groups of two or three; they are small, bright red, bean shaped, and are deposited on the surface of leaves and nuts. One or more eggs are frequently laid in the slight depression near the pointed ends of nuts. Immature bugs (nymphs) are also bright orange-red until about half grown. Infestations persist in almond or- chards until about June 1. Adult boxelder bugs on nuts during May. Samples of Nonpareil meats attacked by box- elder bugs. The nuts on the left are marked by isolated dark kernel spots; meats on the right are more severely damaged. Damage caused by boxelder bugs is two-fold. Small nuts just pushing out of dry jackets wither and drop, while larger nuts which can sustain several bites without withering, suffer internal gum- ming. Stings which pierce the nut to the kernel set up a local reaction. The tender kernel first develops a circular, translu- cent spot which later dries and forms a dark depression. The shell tissue produces a wartlike growth inside the kernel cham- ber. These symptoms are evident only when the nuts are opened for inspection. Most affected nuts show no outward signs of damage but during April some begin to drip gum in long, twisted threads. Crop damage is extensive by this time. The critical period of attack by box- elder bugs extends from about ten days after petal fall until the end of April. Sequences of TEPP sprays in semicon- [12 Leaf-footed plant bug on nut. centrate form or full-volume sprays of parathion give some control. Comparable symptoms of dark kernel spot and fruit gumming are caused by two other related insects : the leaf-footed plant bug, Leptoglossus clypealis Heidm., which on rare occa- sions invades almond orchards during middle spring, and the more prevalent An adult consperse stink bug. consperse stink bug, Euchistus conspersus Uhler, which migrates into orchards dur- ing late May or early June. Adequate spray remedies have not been devised to combat either species. Almond crop losses from nominal infestations of these plant bugs are not critical, however, because most of the damaged kernels are accepted in grade. Scales Important scale insects . . . type of damage . . . identification . . . pesticides As a rule, almonds are reasonably free from the scale insect attacks which devas- tate stone and pome fruits. But local out- breaks on almonds, sometimes of extreme importance, do occur. Scale insects attack young scaffolds and brushwood, reducing vitality, killing local tissues involved in tree growth, reducing the crop, and short- ening the life-span of infested trees (spot- ting of almond fruits by the insects is unimportant). Badly affected limbs drip gum, split as with sunburn, and usually are later killed by wood-boring beetles. Three common species of scales attack almond: San Jose scale, Aspidiotus per- niciosus (Comst.), olive or parlatoria scale, Parlatoria oleae (Colvee), and Eu- ropean fruit lecanium, Lecanium corni Bouche. San Jose and olive scales are much alike in appearance and habit. Both are armored scales; their tiny yel- low (San Jose) or purple (olive) bodies secrete tough, waxy shells (scales) which both protect and camouflage the insects. The slate or gray scales are slightly con- vex and so closely resemble wood pores that they appear to be normal parts of [13] ft . W£ Smooth bark well infested with immature stages of San Jose scale. the bark to which they are permanently attached. Neither adult females nor in- termediate growth stages of these insects move from place to place. During spring months, olive scales lay eggs which accu- mulate in brood chambers beneath their shells. Hatching begins during the latter part of April. San Jose scales begin to reproduce about mid-May. Eggs hatch almost at the instant of laying, or even slightly before, and the young crawlers push out from under the shells of mother scales to become free-living for a brief time. Whether born alive or hatched from eggs, the crawlers scatter to infest new wood or fruit and leaves. When the crawlers settle they develop a permanent attachment to the host, lose their capacity to move from place to place, and gradu- ally form a covering shell. There are two to four generations of crawlers per year. European fruit lecanium, a copious producer of syrupy honeydew, is called an unarmored scale because its outer cov- ering is merely a much-thickened, leath- ery integument of its body wall. Mature females, which develop in spring, are quite large, about 3/16 inch across, con- vex or domed, and brown or mahogany- colored. They are extremely difficult to kill with spray chemicals appropriate for spring use. Their vital organs waste away as eggs accumulate under the arched canopy of body wall. The eggs hatch from May to July, producing only one genera- tion a year. European fruit lecaniums winter as semimature nymphs which can be controlled with dormant sprays. Dur- ing early spring, soon after bloom, these almost naked immature forms quickly harden, hump up, and become rubbery. They are then resistant to pesticides until the brood of young appears. Use of pesticides. Excellent control of European fruit lecanium and San Jose scale can be obtained with dormant oil sprays at concentrations of 3 gallons mis- cible oil or 4 gallons oil emulsion per 100 gallons of water. Oil sprays require suffi- cient rainfall beforehand and should not be applied after floral buds show pink. For olive scale, an added organophosphate is desirable. An optimum dosage includes three gallons oil emulsion (or equivalent emulsive oil) plus two pounds 25 per cent parathion wettable powder, or an op- tional organophosphate insecticide. Spring or summer sprays for scale in- sects are rarely used on almonds. Those which are known to be effective when used on peaches and prunes can be adapted to almonds when registrations for such use are obtained. ri ■■ * i Immature stages of European fruit lecanium on small twig, at the end of winter. [14] Beetles Wood-boring beetles . . . identification . . . control suggestions Sound, vigorous orchard trees are rarely molested by boring beetles. Shot- hole borers usually attack trees already weakened by root diseases, insufficient irrigation, scale insects, chronic mite in- festations or other causes of growth re- tardation. Flat-headed borers are at- tracted to diseased or injured limbs. Es- pecially susceptible limbs are those af- fected by sunburn, scale insects, bacterial canker, mallet wounds, and breaks or major pruning cuts. Very small black beetles called shot- hole borers, Scolytus rugulosus Ratz., burrow into bark to feed and lay eggs. A number of grubs or larvae are produced within this burrow and they, in turn, undermine the bark with secondary gal- leries. The galleries extend radially from the central holes. The entrance or exit holes are cleanly bored, circular, and just under % q inch in diameter. These telltale holes can be numerous on unthrifty limbs. When infestations build up, some of the adults bore into buds or into small twigs at the bases of buds. There are two to three broods each year. Another common boring beetle is the Pacific flatheaded borer, Chrysoboth- ris mali Horn. The full-grown larva of this species is about l 1 /^ inches long, white to flesh-colored, and has a promi- nent, flat enlargement of the body just behind the head parts. The larvae exca- ,-s Branch (apricot) showing shot-hole borer damage. (Photo courtesy Dr. Harold F. Madsen.) vate large, irregularly shaped caverns be- neath injured bark and bore large tun- nels deep into the Sapwood. The excava- tions are usually filled with finely pow- dered sawdustlike matter, so often seen in the cut ends of cordwood. Prevention is the best control. Se- quences of sprays to control wood borers are not practical, but it is possible to abate attacks by pruning out all badly in- fested wood during winter, sealing the cuts, and restoring growth vigor as far as possible. It is advisable to burn infested primings before the growing season starts. Cordwood cut from infested trees should be hauled far away from fruit or- chards before spring. Pesticides Poisonous spray residues . . . danger to human beings . . . contamination of forage hulls Prior to 1949, the outer fleshy cover- ing of the almond fruit — the hull — was a waste product. But during the period 1949 to 1951, it was discovered that almond hulls are of value as food for livestock, particularly lambs and cattle. [15] Acceptance of hulls as animal forage in- troduced complications in pest control, however, and in 1955 the Federal Food, Drug, and Cosmetic Act of 1938 was extended and made more specific by legislation known as the Miller Amend- ment. Since that date permissible con- tamination from residues of poisonous substances has been set very low for forage crops (forage hulls in the case of almonds) to avoid contaminating meat, butter and milk. This greatly restricts the use of pesticides on almonds. Oncoming crops of almonds sometimes require spraying when the fruits are green and heavy. A drying period fol- lows, after which hulls and nuts are sep- arated. Drying and hulling remove much of the weight but leave all or nearly all of the spray residues on the hull por- tion. Thus the contamination originally present on the whole green fruit con- centrates in the dried hulls in direct pro- portion to the amount of drying. Passage through animals introduces a second con- centrating process, and residues origin- ally spread over a large volume of forage hulls may accumulate in the animal tis- sues and, finally, be concentrated in a small volume of fat or milk. Qualified investigators can determine which pesticides present particular haz- ards for stock animals and, ultimately, the human consumers. The "proving out" of new and even old spray chemicals is proceeding slowly, and at present very few materials are registered for use on almonds after the nuts are formed. The list of registered chemicals should grow in time; in the meanwhile the almond producer must bear in mind two salient points: 1. Indiscriminate use of pesticides classed as poisons can jeopardize public health. It is necessary for growers to pro- duce almonds which conform with stand- ards defined by the pure food laws. 2. Almond kernels or meats are much less likely to be contaminated by sprays than are the hulls. Thus certain chemicals may be registered for use on "almonds" but not on "forage hulls." When such materials are applied to green almond fruits the hulls should not be sold for ani- mal forage. A grower is responsible for residues on his own crops. BENEFICIAL ORGANISMS Much work remains to be done on the biological control of almond pests by means of beneficial organisms. A bewil- dering assortment of creatures — such as insects, mites, fungi, and nematodes — comprise a part of each pest's environ- ment. Each one affects one or more of the others, in complex ways, by competition or as parasites or predators. Weather changes and applied agricultural chemi- cals — even fertilizers — induce changes within this living system, whose varia- tions are generally not entirely under- stood by man and, to a great extent, can- not be regulated. Nevertheless, the num- bers of each species, pest or otherwise, rise and fall from time to time, and there are crop years in which certain pests are prevalent, other years when they are not. Entomologists are continually alert for possibilities in biological control, and specialists in this field are sometimes able to find, multiply, and liberate introduced parasites or predators to benefit agricul- turists. Unfortunately, this approach to pest control has not provided solutions to many of the urgent pest problems. Without doubt, the future of pest con- trol will lie not only in developing more useful insecticides but also in acquiring knowledge which will integrate cultural practices, chemical action, and insect population supplements. With this knowl- edge it may be possible to create and maintain a total environmental condition unfavorable for the pests. Co-operative Extension w co-operating. Distributed Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture herance of the Acts of Congress of May 8, and June 30, 1914. George B. Alcorn, Director, California Agricultural Extension Service. 12m-6,'62(CSI L3)A.M.