UNIVERSITY OF CALIFORNIA COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA THE BLACKBERRY MITE, THE CAUSE OF REDBERRY DISEASE OF THE HIMALAYA BLACKBERRY, AND ITS CONTROL E. O. ESSIG BULLETIN 399 December, 1925 UNIVERSITY OF CALIFORNIA PRINTING OFFICE BERKELEY, CALIFORNIA 1925 Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://www.archive.org/details/blackberrymiteca399essi Fig. 1. — Branch of Himalaya, blackberries showing a typical case of the "redberry disease" at the time of harvest. Half natural size. THE BLACKBERRY MITE, 1 THE CAUSE OF REDBERRY DISEASE OF THE HIMALAYA BLACKBERRY, AND ITS CONTROL By E. O. ESSIG* Specimens of Himalaya blackberries infected with what is commonly known as the "redberry disease" were first received by the Division of Plant Patholog3 r during the late summer of 1921. A microscopic examination of the fruit by Miss E. H. Smith, Assistant Plant Pathologist in the Experiment Station, disclosed a minute white mite among the drupelets and, as no other pathogenic organism was discovered, the specimens were placed in my care and I began a study of the problem, to ascertain whether or not the mite was in any way connected with the disease. By conducting some simple spraying tests with lime-sulfur and wettable sulfur on selected plots, it was proved that when the mites were killed the redberry conditions soon disappeared. Successive tests and demonstrations every year since 1921 have shown that the mite was directly responsible for the trouble and that it could be cheaply and effectively controlled. THE HOST PLANT Observations over a period of four years have so far revealed the mite injurious only to the Himalaya blackberry. Other varieties of blackberries, including the Mammoth, Oregon Evergreen, Lawton, as well as dewberries, loganberries and raspberries, growing in the imme- diate vicinity of the Himalaya, and often interlacing with it, have been carefully examined without finding the mite. The Mammoth blackberry frequently develops a redberry condition on a very small scale, but this has usually been due to attacks of mealy bugs, thrips, and other insects. So far, no mites have been found in such berries. NATURE OF THE WORK The work of this mite is best characterized by the common term "redberry disease," which is applied to the red condition of the fruit * Division of Entomology and Parasitology. 1 Eriophyes sp. Family Eriophyidae. 4 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION at harvest time, well shown by the accompanying colored plate (fig. 1). The mites enter the flowers and infest the berries as the drupelets are forming, and remain at the base of the berry and about the core. They feed near the bases of the drupelets, causing abortion in many cases, a retarded and uneven ripening in some, and an abnormal red condition in the great majority of cases (fig. 2). A few berries often remain entirely green or entirely red, while some are to be found with green, red and fully ripened drupelets. This latter condition prevails generally in an infestation of but short duration, and develops into the Fig. 2. — A large crop of Himalaya blackberries with practically 100 per cent infestation of the blackberry mite and none of the berries turning black at time of harvest. (Photo by Paul S. Williamson.) characteristic redberry stage in one or two more years. At this stage, the infested berries remain red for a week or so, then dry up or decay, but never ripen in the normal way. The dried berries may remain on the bushes until the following season (fig. 3). In three or four years an infestation may develop to the extent of ruining the entire crop. A number of commercial patches and many backyard plantings have been rendered absolutely worthless by this obscure mite. In order to observe the mites it is necessary to separate the drupelets of the suspected berries and examine them under a good hand lens or pre- ferably under a microscope, for they cannot be seen by the unaided eye. Bull. 399' THE BLACKBERRY MITE AND ITS CONTROL Fig 3. — Himalaya blackberry infested with the blackberry mite and showing the last season's crop dried and still clinging to the vine on the 18th day of February. (Photo by Paul S. Williamson.) UNIVERSITY OF CALIFORNIA EXPERIMENT STATION THE MITE The mite (fig. 4) responsible for the redberry disease is an unusu- ally small species, averaging but 0.15 mm. in length, and is but one- fifth as wide. The color is translucent white, the form elongated cylindrical, with the anterior region largest and tapering almost to a point at the posterior end. The surface, excepting the fore part, is finely corrugated with seventy-five or eighty fine concentric rings, and supports several long body spines. There are but two pairs of legs, situated anteriorly, which serve to drag the body, the posterior end of which is controlled by means of a sucker which serves as an anchor when needed. The feet terminate in a claw, a plumed hair and a knobbed hair or digitule, as shown in fig. 4. Fig. 4. — The blackberry mite, Eriophyes sp., which is the cause of the "red- berry disease" of the Himalaya blackberry. It is so small that it cannot be seen without a magnifying glass. Greatly enlarged. (Drawing by A. 8. Hassan.) Specimens of the mite forwarded to Dr. H. E. Ewing 2 of the Bureau of Entomology, U. S. Department of Agriculture, were deter- mined as the European species, Eriophyes gracilis (Nalepa), which is common on the European raspberry, Rubus idaeus Linn., in Europe. Nalepa 3 states that it causes a yellow erineum on the tender leaves, but makes no mention of its attacking the fruit. Schlechtendal 4 describes 2 Essig, E. O., and Smith, E. H. Two interesting blister mites. Monthly Bui. California Dept, Agr. 11: 63. 1922. Essig, E. O. Note on the two blister mites. Ibid. 11: 466. 1922. 3 Nalepa, Alfred. Zoologica 24: 236. 1911. 4 von Schlechtendal, D. H. R. Zoologica 24: 414, fig. 15. 1911. BULL. 399] TH E BLACKBERRY MITE AND ITS CONTROL 7 similar work and also gives an illustration of a raspberry shoot show- ing a marked curling of the leaves, with no mention of injury to the berries. It seems hardly probable that the species attacking the ber- ries of the Himalaya blackberry in California is the same as the one infesting the leaves of the European raspberry in Europe, but as yet the writer has been unable to account for its presence in the state. Further study may reveal the true source of its origin. The winter is spent in the leaf clusters and buds, where all the protection possible is available. The hibernators consist of mature and immature forms, which remain inactive until the new growth starts in the spring. As the flower buds appear, the mites work their way into the unfolding buds, into the flowers and down among the developing druplets of the berries, where they feed until the fruit ripens, rots, or dries up on the vines, when all that succeed in making their way to the leaf clusters and buds on the stalks go into hiber- nating quarters. The small white oval eggs are laid in the berries, and several overlapping broods appear during the summer months. DISTRIBUTION The distribution of the blackberry mite in California appears to be coextensive with that of the Himalaya blackberry, which occurs chiefly along the coast (fig. 5). Both appear to thrive best in a cool, moist climate and are most abundant in the San Francisco Bay region and the Santa Cruz foothills. It is doubtful if there is a single com- mercial patch or a backyard vine in the above areas that is not now infested. Infested berries have been received from practically every county along the coast, but serious injury has not yet been recorded in the extreme south or north. CONTROLS Extensive experiments and field demonstrations have proved that the mite can be effectively controlled by the application of early spring sprays and that infestations and injuries may be completely checked by the use of summer sprays. A series of field demonstrations con- ducted by Paul S. Williamson, Assistant Farm Advisor of Santa Cruz County, in commercial plantings, gave excellent proof of the value of the sprays recommended for control. 5 Essig, E. O. Preventing redberry disease. Orchard and Farm, Los Angeles Examiner. Apr. 15, 1923. UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Lcrtituc/e efCetfitOx/ /or. SficAmen,/. %,. 3*N FMHCiSCo 33° N. _ i-aT OiarftsTon, 5 C Fig. 5. — Map of California, showing the coastal region best adapted to the culture of the Himalaya blackberry, and which coincides with the distribution of the blackberry mite and the "redberry disease." BULL. 399] THE BLACKBERRY MITE AND ITS CONTROL 9 Dormant or Early Spring Sprays (fig. 6). — The most satisfactory results are obtained by the application of dormant or early spring sprays to kill the hibernating forms before they gain entrance into the flowers and berries. These sprays consist of commercial lime-sulfur in strengths of 4 per cent, 6 per cent or 8 per cent, or corresponding strengths of dry lime-sulfur or of soluble sulfur. Apparently the 4 per cent is as satisfactory as the stronger solutions if spraying is well done. The improved, highly refined lubricating oil emulsions are also satisfactory. Applications should be made preferably when the new growth starts in the spring and before the flowers open. Pruning and trellising should precede spraying. Great care should be taken to completely cover the stems and buds when spraying. Fig. 6. — Kesults of spraying demonstrations in the control of the blackberry mite in commercial plantings in Santa Cruz County by the Farm Advisor. Fruit sorted at the time of harvest. A, vines sprayed on March 4, 1924, with 4 per cent lime-sulfur; normal berries 484, red berries 16, showing but 3.2 per cent redberry disease when picked on August 4; B, vines sprayed on March 4, with 8 per cent lime-sulfur; normal berries 494, red berries 6, showing but 1.2 per cent redberry disease when picked August 4; C, check vines not sprayed; normal berries 395, red berries 105, showing 21 per cent redberry disease when picked August 4; D, vines sprayed May 4 with 4 per cent lime-sulfur; normal berries 487, red berries 13, showing 2.6 per cent redberry disease ; E, vines sprayed July 7 with five pounds of wettable sulfur to one hundred gallons of water; normal berries 474, red berries 26, showing 4.2 per cent redberry disease. (Photo by Paul S. Williamson.) 10 UNIVERSITY OF CALIFORNIA EXPERIMENT STATION Blossom and Summer Sprays. — Later spring sprays of either 4 per cent lime-sulfur or of wettable sulfur, applied when the vines are in full bloom, are nearly as effective as the dormant sprays, according to the demonstrations conducted by Mr. Williamson in Santa Cruz County. The usual strength of wettable sulfur spray is five pounds of wettable sulfur to one hundred gallons of water. In cases of severe infestations, eight pounds of the wettable sulfur may be used. Summer spraying, if done when the berries are still green, may result in check- ing the work of the mites and thus allow some of the berries to mature normally. Late fall spraying is often too late to affect the crop of the same year but will destroy many of the mites and thus help to control the pest the next season. Summer or fall spraying, followed by dor- mant spring sprays, will insure complete protection. To prepare wettable sulfur sprays, mix dry ten pounds of milled sulfur or flowers of sulfur and one-half pound of dry calcium caseinate spreader. Add sufficient water to make a paste. Place in the spray tank and add the remainder of the water to make the proper dilution. Spraying Insurance. — This is one case where spraying as insurance may be justly advocated because the mite is so generally distributed and control measures are so sure to bring the desired results that the berry grower cannot afford to run the risk of losing even a part of the crop by failing to properly treat the plants in the early spring. Spray Injury. — So far, no injury- to the vines or berries has been noticed from dormant and blossom sprays, even where the concentra- tion of lime-sulfur has been as high as 8 per cent. Summer sprays of wettable sulfur, however, have caused some burning to the leaves and fruit when used stronger than four pounds to one hundred gallons of water. To avoid spray injury, apply only dormant or early spring sprays, or irrigate, if possible, before the application of summer sprays, and do not spray during excessively dry and hot weather. CONSUMPTION OF INFESTED BERRIES Infested berries are in no way injurious for human consumption. If they are not edible fresh, because of lack of ripening, they may be safely used for jams and jellies. STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION BULLETINS No. 253. 261. 262. 263. 268. 273. 275. 277, 278. 279, 280, 283, 285. 294. 304, 310. 312. 313. 319. 324. 325. 328. 331, 334, 335. 339. 340. 343. 344. 346. 347. 348. 349. 350. 352. 353. 354. 357. 358. 359. No. Irrigation and Soil Conditions in the 361. Sierra Nevada Foothills, California. Melaxuma of the Walnut, "Juglans 362. regia." ■ 363. Citrus Diseases of Florida and Cuba Compared with Those of California. 364. Size Grades for Ripe Olives. Growing and Grafting Olive Seedlings. 365. Preliminary Report on Kearney Vine- 366. yard Experimental Drain. The Cultivation of Belladonna in 367. California. The Pomegranate. 368. Sudan Grass. Grain Sorghums. 369. Irrigation of Rice in California. Irrigation of Alfalfa in the Sacra- 370. mento Valley. 3 71. The Olive Insects of California. The Milk Goat in California. 372. Bean Culture in California. A Study of the Effects of Freezes on 373. Citrus in California. 374. Plum Pollination. Mariout Barley. Pruning Young Deciduous Fruit 375. Trees. Caprifigs and Caprification. 376. Storage of Perishable Fruit at Freez- ing Temperatures. 377. Rice Irrigation Measurements and 379. Experiments in Sacramento Valley, 380. 1914-1919. Prune Growing in California. 381. Phylloxera-Resistant Stocks. Preliminary Volume Tables for Sec- 382. ond-Growth Redwood. Cocoanut Meal as a Feed for Dairy 383. Cows and Other Livestock. The Relative Cost of Making Logs 384. from Small and Large Timber. Control of the Pocket Gopher in California. Cheese Pests and Their Control. 385. Cold Storage as an Aid to the Mar- 386. keting of Plums. Almond Pollination. 387. The Control of Red Spiders in Decid- 388. uous Orchards. Pruning Young Olive Trees. 389. A Study of Sidedraft and Tractor 390. Hitches. Agriculture in Cut-over Redwood 391. Lands. Further Experiments in Plum Pollina- 392. tion. 394. Bovine Infectious Abortion. Results of Rice Experiments in 1922. 395. A Self-mixing Dusting Machine for 396. Applying Dry Insecticides and Fungicides. 397. Black Measles, "Water Berries, and Related Vine Troubles. 398. Fruit Beverage Investigations. Preliminary Yield Tables for Second Growth Redwood. Dust and the Tractor Engine. The Pruning of Citrus Trees in Cali- fornia. Fungicidal Dusts for the Control of Bunt. Avocado Culture in California. Turkish Tobacco Culture, Curing and Marketing. Methods of Harvesting and Irrigation in Relation of Mouldy Walnuts. Bacterial Decomposition of Olives dur- ing Pickling. Comparison of Woods for Butter Boxes. Browning of Yellow Newtown Apples. The Relative Cost of Yarding Small and Large Timber. The Cost of Producing Market Milk and Butterfat on 246 California Dairies. Pear Pollination. A Survey of Orchard Practices in the Citrus Industry of Southern Cali- fornia. Results of Rice Experiments at Cor- tena, 1923. Sun-Drying and Dehydration of Wal- nuts. The Cold Storage of Pears. Walnut Culture in California. Growth of Eucalyptus in California Plantations. Growing and Handling Asparagus Crowns. Pumping for Drainage in the San Joaquin Valley, California. Monilia Blossom Blight (Brown Rot) of Apricot. A Study of the Relative Values of Cer- tain Succulent Feeds and Alfalfa Meal as Sources of Vitamin A for Poultry. Pollination of the Sweet Cherry. Pruning Bearing Deciduous Fruit Trees. Fig Smut. The Principles and Practice of Sun- drying Fruit. Berseem or Egyptian Clover. Harvesting and Packing Grapes in California. Machines for Coating Seed Wheat with Copper Carbonate Dust. Fruit Juice Concentrates. Cereal Hay Production in California. Feeding Trials with Cereal Hay. Bark Diseases of Citrus Trees. The Mat Bean (Phaseolus aconilifo- lius). Manufacture of Roquefort Type Cheese from Gnat's Milk. Orchard Heating in California. CIRCULARS No. No. 87. Alfalfa. 154. 113. Correspondence Courses in Agriculture. 117. The Selection and Cost of a Small 155. Pumping Plant. 157. 127. House Fumigation. 160. 129. The Control of Citrus Insects. 164. 136. Melilotus indica as a Green-Manure 165. Crop for California. 144. Oidium or Powdery Mildew of the 166. Vine. 167. 151. Feeding and Management of Hogs. 170. 152. Some Observations on the Bulk Hand- ling of Grain in California. Irrigation Practice in Growing Small Fruit in California. Bovine Tuberculosis. Control of the Pear Scab. Lettuce Growing in California. Small Fruit Culture in California. Fundamentals of Sugar Beet Culture under California Conditions. The County Farm Bureau. Feeding Stuffs of Minor Importance. Fertilizing California Soils for the 1918 Crop. No. 173. 178. 179. 184. 190. 199. 202. 203. 209. 210. 212. 214. 215. 217. 220. 228. 230. 231. 232. 233. 234. 235. 236. 237. 238. 239. 240. 241. 242. 243. 244. 245. 247. 248. 249. 250. 251. 252. 253. 254. 255. CIRCULARS — (Continued) No. The Construction of the Wood-Hoop Silo. The Packing of Apples in California. Factors of Importance in Producing Milk of Low Bacterial Count. A Flock of Sheep on the Farm. Agriculture Clubs in California. Onion Growing in California. County Organizations for Rural Fire Control. Peat as a Manure Substitute. The Function of the Farm Bureau. Suggestions to the Settler in California. Salvaging Rain-Damaged Prunes. Seed Treatment for the Prevention of Cereal Smuts. Feeding Dairy Cows in California. Methods for Marketing Vegetables in California. Unfermented Fruit Juices. Vineyard Irrigation in Arid Climates. Testing Milk, Cream, and Skim Milk for Butterfat. The Home Vineyard. Harvesting and Handling California Cherries for Eastern Shipment. Artificial Incubation. Winter Injury to Young Walnut Trees during 1921-22. Soil Analysis and Soil and Plant Inter-relations. The Common Hawks and Owls of California from the Standpoint of the Rancher. Directions for the Tanning and Dress- ing of Furs. The Apricot in California. Harvesting and Handling Apricots and Plums for Eastern Shipment. Harvesting and Handling Pears for Eastern Shipment. Harvesting and Handling Peaches for Eastern Shipment. Poultry Feeding. Marmalade Juice and Jelly Juice from Citrus Fruits. Central Wire Bracing for Fruit Trees. Vine Pruning Systems. Colonization and Rural Development. Some Common Errors in Vine Prun- ing and Their Remedies. Replacing Missing Vines. Measurement of Irrigation Water on the Farm. Recommendations Concerning the Com- mon Diseases and Parasites of Poultry in California. Supports for Vines. Vineyard Plans. The Use of Artificial Light to Increase Winter Egg Production. Leguminous Plants as Organic Fertil- izer in California Agriculture. 256. 257. 258. 259. 260. 261. 262. 263. 264. 265. The Control of Wild Morning Glory. The Small-Seeded Horse Bean. Thinning Deciduous Fruits. Pear By-products. A Selected List of References Relating to Irrigation in California. Sewing Grain Sacks. Cabbage Growing in California. Tomato Production in California. Preliminary Essentials to Bovine Tuberculosis Control. Plant Disease and Pest Control. 266. Analyzing the Citrus Orchard by Means of Simple Tree Records. 267. The Tendency of Tractors to Rise in Front; Causes and Remedies. 268. Inexpensive Labor-saving Poultry Ap- pliances. 269. An Orchard Brush Burner. 270. A Farm Septic Tank. 2 71. Brooding Chicks Artificially. 272. California Farm Tenancy and Methods of Leasing. 273. Saving the Gophered Citrus Tree. 274. Fusarium Wilt of Tomato and its Con- trol by Means of Resistant Varieties. Marketable California Decorative Greens. Home Canning. Head, Cane, and Cordon Pruning of Vines. Olive Pickling in Mediterranean Coun- tries. The Preparation and Refining of Olive Oil in Southern Europe. The Results of a Survey to Determine the Cost of Producing Beef in Cali- fornia. Prevention of Insect Attack on Stored Grain. Fertilizing Citrus Trees in California. The Almond in California. Sweet Potato Production in California. Milk Houses for California Dairies. Potato Production in California. Phylloxera Resistant Vineyards. Oak Fungus in Orchard Trees. 275. 276. 277. 278. 279. 281. 282. 283. 284. 285. 286. 287. 288. 289. 290. The Tangier Pea. 291. Blackhead and Other Causes of Loss of Turkeys in California. 292. Alkali Soils. 293. The Basis of Grape Standardization. 294. Propagation of Deciduous Fruits. 295. The Growing and Handling of Head Lettuce in California. 296. Control of the California Ground Squirrel. 297. A Survey of Beekeeping in California; The Honeybee as a Pollinizer. 298. The Possibilities and Limitations of Cooperative Marketing. 299. Poultry Breeding: Records. 300. Coccidiosis of Chickens. The publications listed above may be had by addressing College of Agriculture, University of California, Berkeley, California. 10m-12,'25