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UNIVERSITY OF CALIFORNIA PUBLICATIONS COLLEGE OF AGRICULTURE AGRICULTURAL EXPERIMENT STATION BERKELEY, CALIFORNIA CITRUS FRUIT INSECTS By H J QUAYLE BULLETIN No (Berkeley, Cal May, 214 1911) SACRAMENTO W W SHANNON - - - - SUPERINTENDENT OP STATE PRINTING 1911 EXPERIMENT STATION STAFF E E Wickson, M.A., Director and Horticulturist Ph.D., LL.D., Chemist (Emeritus) W A Setchell, Ph.D., Botanist Leroy Anderson, Ph.D., Dairy Industry and Superintendent University Farm Schools M E Jaffa, M.S., Nutrition Expert, in charge of the Poultry Station R H Loughridge, Ph.D., Soil Chemist and Physicist (Emeritus) C W Wood worth, M.S., Entomologist Ralph E Smith, B.S., Plant Pathologist and Superintendent of Southern California Pathological Laboratory and Experiment Station G W Shaw, M.A., Ph.D., Experimental Agronomist and Agricultural Technologist, in charge of Cereal Stations E W Major, B.Agr., Animal Industry, Farm Manager, University Farm, Davis F T Bioletti, B.S., Viticulturist B A Etcheverry, B.S., Irrigation Expert George E Colby, M.S., Chemist (Fruits, Waters, and Insecticides), in charge of J W Hilgard, Chemical Laboratory Quayle, M.S., Assistant Entomologist, Plant Disease Laboratory, Whittier W T Clarke, B.S., Assistant Horticulturist and Superintendent of University ExtenH J sion in Agriculture H M Hall, Ph.D., Assistant Botanist C M Haring, D.V.M., Assistant Veterinarian and Bacteriologist John S Burd, B.S., Chemist, in charge of Fertilizer Control E B Babcock, B.S., Assistant in Agricultural Education W B Herms, M.A., Assistant Entomologist J H Norton, M.S., Assistant Chemist, in charge of Citrus Experiment Station, Riverside W T Horne, B.S., Assistant Plant Pathologist J E Coit, Ph.D., Assistant Pomologist, Plant Disease Laboratory, Whittier C B Lipman, Ph.D., Soil Chemist and Bacteriologist R E Mansell, Assistant in Horticulture, charge of Central Station grounds A J Gaumnitz, M.S., Assistant in Cereal Investigations, University Farm, Davis E H Hagemann, Assistant in Dairying, Davis B S Brown, B.S.A., Assistant in Horticulture, University Farm, Davis F D Hawk, B.S.A., Assistant in Animal Industry J I Thompson, B.S., Assistant in Animal Industry, Davis R M Roberts, B.S.A., Field Assistant in Viticulture, University Farm, Davis m Bridwell, Entomologist in Agricultural Chemical Laboratory Sylviculture, Santa Monica E H Smith, M.S., Assistant Plant Pathologist T F Hunt, B.S., Assistant Plant Pathologist C O Smith, M.S., Assistant Plant Pathologist, Plant Disease Laboratory, Whittier F L Yeaw, B.S., Assistant- Plant ^Pathologist, Vacaville F E Johnson, B.L., M.S., Assis'tanVin Soil Laboratory Charles Fuchs, Curator Entomological Museum P L Hibbard, B.S., Assistant in Fertilizer Control Laboratory L M Davis, B.S., Assistant in Dairy Husbandry, University Farm, Davis L Bonnet, LA., Assistant in Viticulture Plant Pathologist, Plant Disease Laboratory, Whittier S S Rogers, B.S., Assistant B A Madson, B.S.A., Assistant in Cereal Laboratory Walter E Packard, M.S., Field Assistant, Imperial Valley Investigation, El Centre M E Stover, B.S., Assistant in Agricultural Chemical Laboratory P L McCreary, B.S., Laboratory Assistant in Fertilizer Control E E Thomas, B.S., Assistant Chemist, Plant Disease Laboratory, Whittier Anna Hamilton, Assistant in Entomology Mrs D L Bunnell, Secretary to Director W H Volck, Field Assistant in Entomology, Watsonville E L Morris, B.S., Field Assistant in Entomology, San Jose J S Hunter, Field Assistant in Entomology, San Mateo J C Roper, Patron, University Forestry Station, Chico J T Bearss, Foreman, Kearney Park Station, Fresno MILLER, Foreman, Forestry Station, Chico J C B.S., Assistant McCharles, B.S., Assistant N D Ingham, B.S., Assistant in C H CONTENTS INTRODUCTION Page THE BLACK SCALE 445 449 451 452 (Saissetia oleae Bern.) Life history Seasonal history Distribution and spread Parasites and predaceous enemies Scutellista cyanea Motsch Other enemies 456 459 459 Control THE RED OR ORANGE SCALE (Chrysomphalus aurantii Mask.) Life history Seasonal history Food plants Distribution and spread Parasites Aphelinus diaspides How 459 460 462 463 463 463 Predatory enemies Rhizobius Lophanthw Blaisd THE YELLOW SCALE Distribution Life history Parasites Control 464 (Chrysomphalus aurantii 465 465 465 465 466 var citrinus Coq.) ± THE PURPLE SCALE (Lepidosaphes beckii Newm.) 466 466 468 469 469 Life history Seasonal history Natural enemies Control THE COTTONY CUSHION SCALE (Icerya purchasi Mask.) Present status in California Life history annd habits Natural enemies SOFT BROWN SCALE (Coccus hesperidum Linn.) Life history Natural enemies HEMISPHERICAL SCALE (Saissetia hemisphaerica Targ.) Natural enemies THE GREEDY SCALE (Aspidiotus rapax Comst.) THE OLEANDER SCALE (Aspidiotus hederae Comst.) THE CITRUS MEALY BUG Life history and habits Natural enemies Control (Pseudococcus citri Risso.) 469 470 472 472 475 476 476 478 478 480 481 481 483 484 484 CONTENTS— Continued RED SPIDERS (Tetranychus mytilaspidid Riley) (Tetranychus sexmaculatus Riley )_: Life history and habits Control SILVER MITE Page 485 485 486 487 489 489 490 (Phytoptus oleivorus Ash.) Life history and habits Control THRIPS 490 493 493 Life history and habits Control APHIS (Aphis gossypii) THE ORANGE TORTRIX 493 (Tortrix citrana Fern.) Life history and habits FULLER'S ROSE BEETLE - (Aramigus fulleri Horn.) Life history, habits and control DIABROTICA SOROR SERIOUS CITRUS FRUIT PESTS NOT YET ESTABLISHED IN CALIFORNIA The Orange Maggot (Trypeta ludens Loew.) The Citrus White Fly (Alerodes citri R and H.) 494 495 499 499 501 503 503 504 SPRAYING FOR CITRUS FRUIT INSECTS 505 FUMIGATION 506 INSPECTION AND QUARANTINE 511 CITRUS FRUIT INSECTS By H J Quayle INTRODUCTION That insect pests are one of the important factors in the citrus fruit is shown by the fact that more than This half a million dollars are expended annually in their control amount includes only what is actually expended in fumigation and spraying, and does not take into consideration the loss of fruit from imindustry of southern California properly treated trees or trees not treated at in one county alone amounts all The to $200,000 annually cost of fumigation Furthermore, each county maintains a horticultural commissioner, and many of them a corps of inspectors, primarily on account of insect enemies, who are charged with the quarantine and inspection work, the cost of which in some of the counties may run as high as $25,000 annually That all of this vigilance is necessary seems to be warranted from the thirty years experience of the most important citrus fruit section of the United States It has been estimated that the average cost of fumigation per tree, belt, amounts to about 30 or 40 cents, which means an expense of approximately $30 to $40 per acre, and this is done on an average about every other year This is intensive insect fighting, but w hen the improved market value of the fruit is considered, it is money judiciously spent with such a valuable crop as the orange or taking the whole of the citrus T lemon Commercial citrus culture in California is confined to seven counties south of the Tehachapi mountain range, namely, Santa Barbara, Ven- Los Angeles, Orange, Riverside, San Bernardino, and San Diego and the two counties north of this range, namely, Tulare in the upper San Joaquin Valley, and Butte in the upper Sacramento Valley The southern counties form a section contiguous to the coast line, and which has a coast climate, excepting the Riverside-Redlands district, which approaches the interior conditions on account of its distance from the ocean (60 to 75 miles), without being separated by a w ell-defined natural barrier The San Joaquin and Sacramento Valley citrus districts have the typically interior climate which is characterized by hotter summers than that of the more equable coast counties These general climatic differences appear to account for the differences in the insect pests, not only of the northern and southern sections, but also within the latter section itself, since even here there is a wide range of variation However, it is not safe to speak too confidently of the influence of climate on insect distribution Time has changed a numtura, T UNIVERSITY OF CALIFORNIA 444 EXPERIMENT STATION ber of ideas to correspond with the facts as they exist to-day It had been asserted that California need have no fear of the citrus white fly, yet this pest got a fairly good foothold in a part of the State least unsuited to would not it, according to theory was also held that the black scale exist in the Riverside section, yet citrus trees it occurs there and attacks Likewise, the purple was supposed not to become a pest in arid California, and, if to a It narrower range than In general, however, it it its did become established, it would be limited distribution at the present time indicates may be said that the black scale thrives best shown by its prevalence in the citrus belt San Diego, and also on deciduous trees in the The interior valley citrus sections are not coast counties of the north troubled with the black scale, though it may occur there on such plants The purple scale, thus far, is limited to the as the olive and oleander coast counties, occurring with the black, but not of such wide distribution The red and yellow scales occur both near the coast and in the interior, though they are considered the more typical scales of the warmer interior sections Aside from the scale insects mentioned, the next most general citrus tree pests are to be found among the spiders and mites The Florida red spider and the six-spotted mite are widely distributed, while the silver mite of the lemon is restricted to a limited section in San Diego County The mealy bug has become a rather serious pest in certain limited sections in Ventura and San Diego counties, and also smaller The soft brown, cottony cushion, and a infestations in other counties few other scales sometimes occur in considerable numbers over small areas, but are not usually considered permanent pests A species of thrips has recently come into prominence as a pest in the San Joaquin The orange tortrix is the only insect that burrows into the section orange itself to any extent, and this fortunately has not become a very important pest thus far Other insects which attack the fruit occasionally are grasshoppers, katydids and cutworms Other biting insects attacking the leaves only are Fuller's rose beetle and the common in sections' near the coast, as from Santa Barbara to Diabrotica A couple of dozen species will thus cover all the insects of economic importance attacking citrus trees in California, and of these, practically all of the control work is directed against but four of the scale insects, the black (Saissetia olece Bern.), the red (Chrysomphalus aurantii Mask.), the yellow (Chrysomphalus aurantii var citrinis Coq.) and the purple (Lepidosaphes beckii Newm.) The present publication is intended to give a popular account of all those species likely to be considered of economic importance, together with their chief attendant parasites or enemies and This will include a discussion of their life habits, mainly, since the principal reliance for control, history which is Bulletin 214] fumigation, is discussed in separate publications from this station and Department also the fumigation 445 CITRUS FRUIT INSECTS A Washington at brief outline of spraying and however, appended at the close of this bulletin which gives is, The control the essential facts for these operations are not handled by fumigation or spraying is of those pests which given at the close of the discussion of each species Most of the photographs were made by Professor R W Doane of Stanford University, who assisted in the investigation of citrus fruit insects during the summer of 1910, while the drawings are the work of Miss Anna Hamilton THE BLACK SCALE (Saissetia olece Bern.) The Black Scale southern of pests (Saissetia olece Bern.) ranks first among the citrus California This statement is based upon the amount of control work actually directed against it, and its wide distribution throughout the rus belt the mealy cit- The purple scal,e and bug may be more diffi- cult insects to control, but their distribution is not so general as In the county horticultural commissioners reports tabulated on next page, the that of the black ' black scale is given first place in three counties, Los Angeles, San- and Orange The second in two others, Ventura and San Diego While the mealy bug ta Barbara, is given place in Ventura, first will be noticed that it most of the work is against the black This scale also has a wider dis- control San Diego County and should tribution in than the probably purple, be place there is to control first work directed against the purple, and the black it, entitled Where Fig -Black Scale (Saissetia oleae Bern.) on orange twig is associated with the extra dosage used against the former keeps the black well in check, otherwise it would have to be reckoned with separately The UNIVERSITY OF CALIFORNIA 446 —EXPERIMENT STATION TABULAR STATEMENT CONCERNING CITRUS INSECT PESTS BY COUN I Most important Riverside San Bernardino R P Cundiff Commissioner A Pease, Commissioner A R Meserve, Commissioner Roy K Bishop, Red Red Black Black Yellow Yellow Red Red Black Black Purple Purple $75,000 $200,000 $175,000 $35,000 5,000 1,000 Third ant rv Annual cost fumigating V Annual cost spraying 8,000 10,000 VI Annual cost fumigating 10 years ago 20,000 60,000 5,000 25,000 IX Annual cost spraying 1_~ 10 years ago Proportion of fumigating and spraying for black scale Proportion *30-40% Proportion ing for XI and 33J% Nearly all 60-70% fumigatspraying No purple purple in county No purple in county Acreage citrus in fruits 10 years ago Present XII XIII Commissioner fumigatspraying and ing for red and yellow _ X Orange most import- III VIII Angeles Seond most important VII Los scale insect pest II S acreage 16,000 Other control work N cardinalis for cottony cushion C Lecanii for soft brown 75% for black in 1910 24,000 17,800 57,000 29,200 Spraying for Mealy bug red spiders pest in certain sec- tions 12,500 Sulfur for red spider, Bulletin 214] TIES GIVEN 447 CITRUS FRUIT INSECTS BY THEIR RESPECTIVE HORTICULTURAL COMMISSIONERS San Diego Ventura H Santa Barbara W Butte Tulare A G Schulz Commissioner Commissioner Commissioner Commissioner Earle Mills Commissioner Citrus mealy Purple Black Yellow Black Purple Soft brown E Essig, C Stuart, C Beers bug Black Long-tailed Citrus Work just begun 3,000 mealy Yellow bug mealy bug None $10,000 None of the economic $1,500 scales lished 1908-9, 1909-10, 10,000 1910-11, 20,000 cial None, except for mealy bug No fumigation One orchard 1,000 None 2,000 Same as to-day No records None Same as to-day No records None then Practically all None 50% None in cial Only two infesta- commer- orchards 100% None tions in county 1-16 None 50% No purple in county • 10,000 12,000 Lime-sulfur for red spider Predaceous enemies: cottony cushion and mealy bug 7,000 Scutellista does good work some years Also cryptolaemes on mealy bugs 1,400 1,200 13,000 1,800 Parasites control Black Parasites give excellent control of purple commer- acres sprayed for thrips in 1910 spray then No fumigation estab- yet in groves Parasites and predatory enemies for cottony cushion and soft brown 448 EXPERIMENT STATION UNIVERSITY OF CALIFORNIA only sections where the black is not considered a serious pest in the south are certain sections of Riverside and San Bernardino counties The chief injury occasioned by the black scale is not due so much to the loss of sap through feeding, nor due is it to the poisonous effect on the mouth parts The black scale excretes large quantities of so-called honey dew which falls upon the upper surface of the leaves and fruit, and this serves as a medium for the growth of a fungus known as the sooty mold fungus plant tissues through the insertion of its thread-like This necessitates the washing of the fruit, which operation alone adds is due to the wash infected with blue mold becoming and other fungi Since the water fruit comes in contact with the sides of the tank, brushes, elevators, and to the cost of the handling, but the chief injury Fig —Mature Black Scales drying racks, it is impossible to escape some abrasion of the fruit, into which the spores of the fungus readily make their way Regarding the washing of oranges, Powell in Bulletin 123 of the Bureau of Plant Industry, U S D A., says the following: Oranges are washed primarily to remove the sooty mold fungus that grows in the so-called honey dew exuded by the black scale (Saissetia ' ' Bern.) The Valencia orange is sometimes washed to raise the grade by making the fruit clean and attractive, and the Washington Navel is occasionally washed with that end in view olece "When the present investigation by the Bureau of Plant Industry was undertaken, from one third to one half of the oranges of California were washed, practically all the fruit in some sections being treated in this way, especially where the growers had been over-confident in the parasite Scutellista cyanea Motsch, or in the use of oil sprays as a means of holding the black scale in check." More Scales detailed ;in«l complete publications will follow on the Black, Red and Purple 500 UNIVERSITY OF CALIFORNIA Fig 62 Fig 63 — Small EXPERIMENT STATION —Work of Fuller's rose beetle on orange leaves orange trees banded with cotton for protection against Fuller's rose beetle 501 CITRUS FRUIT INSECTS Bulletin 214] Fig 64 —Work of white ants in orange wood DIABROTICA SOROR to be the familiar green beetle with twelve black spots that is much damage seen everywhere and on all sorts of plants It often does foliage is lemon The orange the of to the tender, growing shoots This is In a grove where orange and lemon trees were but rarely attacked planted alternately, it was ob- served that no noticeable injury occurred on the lemon, young growth of the orange was severely attacked In the case of budded the while all trees, they are specially likely from the attacks of Diabrotica The larva is subterranean and feeds on several to suffer «ffi?.y