DeBach, Paul : Division of Biological Control, Department of Entomology

Riehl, Louis A. : Emeritus, Department of Entomology

Treatment Guidefor CalaYornia Citrus Crops Insect pests and ( published by the Division of Agricultural Scien - ces , University of California , Berkeley ) . Among their control materials developed and recommended against 29 pests are parathion for California red scale and Louis A . Riehl , Professor of Entomology , Emeritus , citricola scale , trichlorfon for several orange - Department of Entomology , and worms , oxythioquinox for citrus red mite , chloro - Paul DeBach , Professor of Biological Control and benzilate for citrus bud mite , and dimethoate for Entomologist , Division of Biological Control , has been a citrus thrips . Resistance in some pests Department of Entomology recurring problem , requiring testing and develop - ment of new materials . Research will continue to update the guide . niversity research on insects and mites on With the development of organic chemicals citrus began in southern California in 1906 U came increased interest in residues of these with the appointment of H.J . Quayle to the materials in commodities.Studies were begun to Disease Laboratory at Whittier . In 1916 U.C . Plant determine residues of insecticides and acaricides he correctly attributed resistance of black scale on treated crops , their degradation , and other and California red scale to fumigation with HCN - aspects . Residue data became an integral part of one of the first reports of resistance . Quayle investigations before recommendation of a mater - moved to Riverside in 1917 , and the Division of ial . The U.C . residue group played an1 important Entomology of the Citrus Experiment Station was role worldwide in developing safety standards formed in 1918 . Professor Quayleâ??s studies on citrus insects and mites and their control brought A . Oscillating boom ap - worldwide recognition . plying dilute spray . Control problems spurred research on petroleum oil , a little - known and unpredictable material . The B . Adult female Cali - first breakthrough came in 1914 with the discovery fornia red scale . that acute idury to foliage could be prevented by C . Aphytis rnelinus para - treating the oil with sulfuric acid ; this was the site laying eggs in Cali - basis for the specification of 92 percent minimum fornia red scale . â?? unsulfonated residue ( U.R . ) that has been the standard of safety to fruit trees for spray oils since D . Cales noacki parasite 1932 . The formulations in use created â?? tight â?쳌 of woolly whitefly . emulsions with low rates of deposit that required 10 to 13percent oil . In 1927the concentrations of E . Parasitization of a quick - breakingconcept of formulation with higher heavy infestation of deposit rates was developed ; this gave better con - woolly whitefly on a leaf by Amitus spiniferus , as trol with reductions of nearly tenfold in the con - shown by the exit holes This centration of oil in the dilute spray mixtures . of the parasite . concept is still basic to spray oil formulation . Then came the classic work on the relation of oil distil - F . Female citrus red mite . lation data to pest control and effect on trees . These results were used to form specifications adopted by California in 1932for registration and labeling of spray oils . Some problems of effects on the fruit remained , however . Investigations led to the development in a 1965 of the narrow - range ( N - R ) 415 - type oil , spray oil that could be used on oranges ( particu - larly navels ) in September against citrus red mite and California red scale without adverse effects on the fruit . Also , its narrow range meant that the oil could be used in low - volume application against citrus red mite . However , for such use in hotter as August , the N - R 440 - type oil , with months such larger molecules , was developed . Both of the N - R oils are useful in IPM programs for citrus . Two other developments important in the safer use of oil spray are ( 1 ) adding 2,4 - D to oil spray to pre - vent leaf and fruit drop and ( 2 ) application of gib - berellin to prevent water spot of navel oranges . In the late 1930s , work on mites of citrus and walnuts developed the first successful organo - chemicalacaricide , a dinitrophenol compound that was the forerunner of the organochemicalpesti - in the 1950s.In 1956 , as a means cides burgeoning of giving this new information to growers , a pub - lication of recommended treatments against in - sectsand mites on citrus was begun , now entitled CR - 13 concerning pesticides in foods . With rising concern for the first time anywhere , of those species as primary para - whose females develop normally for workers , research by the group developed basic and practical information on hazards of resi - as hyperparasites - sites but whose males develop that is , upon other parasites . dues , on the posttreatment interval necessary for reentry by workers having contact with treated Perhaps the most important ecological principle foliage , and on conditions and amounts of expo - in applied biological control is importation of as sure during application work . many natural enemy species as possible , as op - posed to singling out the one most effective The shortage of workers in the 1940s sparked natural enemy . This principle was first proposed , development of machines with spray application booms . By 1951a new pump provided the volume tested , and demonstrated at Riverside . Competi - tion may eliminate some , but the best individual or and force needed for a boom ; mechanical oscilla - tion moved the spray guns in a circular pattern . complex survives to effect the maximum biological control possible from the total natural enemy com - Related studies at Riverside provided information on operation and calibration . An experimental plex originally colonized in the field . Most workers now follow this precept . procedure was devised to quantitatively measure the coverage of citrus trees ; later modifications Experimental methods of evaluating the effec - tiveness of natural enemies were first emphasized enabled measurement of coverage by low - volume at Riverside . All of this basic research has led to sprayers . more successes in biological control of citrus pests Studies of low - volume sprayers culminated in in Californiathan has been achieved with any models with two sets of spray discharge heads - other crop in any other country . Many of these lower and upper - joined by a vertical air tower , results have been used in other regions . which gave satisfactory coverage of citrus trees . Foreign exploration for new natural enemies has The low - volume sprayer is important , because sav been vigorously pursued , once basic research has ings in application costs are substantial and the given the explorer key information on where to go physical aspects of the spray do not affect natural and how to search . Techniques of bringing back enemies . the natural enemies have been developed and Continuing research on fumigation included studies of commodity treatments of citrus and greatly refined . 1920s the citrophilus mealybug In the early avocados , which now provide the information spread rapidly , becoming a catastrophic pest of basic to export shipment under quarantine restric - 1927 , 100,000 citrus in southern California . By tions . acres were heavily infested , and chemical treat - Use of a granular formulation to control ants ments , periodic mass release of the ladybeetle was developed with chlordane ; its ban has been offset by the development at Riverside of two ( Cryptolamusmontrcumieri Mulsant ) and even replacement chemicals , diazinon and chlorpyrifos . expensive , high - pressure water - washing were in - effective . The Citrus Experiment Station sent H . The ban of calcium arsenate removed an effective , low - cost bait for control of the brown garden Compere to Australia in the summer of 1927 to search for the mealybug and possible natural ene - snail , but research has replaced it with the metal - dehyde and methiocarb bait . mies . England and South Africa were known to have been invaded by the mealybug , and it was assumed that the pest had originated in a subtrop - Biological control ical climate linked by steamer to those two coun - tries and southern California . Australia was Biologicalcontrol research in the University of considered to be the most likely country , even 1923 at the Citrus Experiment Californiabegan in though the citrophilus mealybug had not been Station , when H.S . Smith and the biological con - recorded there . trol unit of the State Commission of Horticulture were transferred to Riverside . The more scientific This detective work paid off . In Sydney , early in 1928 , Compere found a heavily infested mulberry bio - ecologicalapproach delineated important char - acteristics of effective natural enemies and their tree , which produced an abundance of parasites . He immediately decided to return with this mater - role in pest population regulation . This approach ial to California by steamer ; the three - week trip shifted emphasis from natural enemies that feed necessitated culturing the mealybug and parasites on a variety of hosts to more specific ones highly on potatoes in a vacant hospital room en route . At adapted to a particular host ( pest ) and having the Riverside , the insects were cultured in large high searching ability required to keep the host at 1928 and released numbers during March to May low population densities . in the field throughout southern California . The importance of taxonomy in distinguishing Coccophaqm The two parasite species involved , between closely related natural enemy species or even races was recognized early . This has made possible the discovery and importation into Cali - fornia of a considerable number of reliable para - sites of citrus pests that , otherwise , would have remained unknown . Intricate biologies of various parasites of citrus scales and mealybugs were first worked out at Riverside ; the result was laboratory culture and subsequent colonizationin the field , CR - 14 gumeyi Compere and Arhopoideus ( = Tetrame - brown soft scale , brown citrus aphid , Bakerâ??s mus ) pretiosus ( Timberlake ) , increased and spread mite . mealybug , greedy scale , and the citrus red rapidly , effecting complete control by 1930 . Since U.C . , Riverside , research has demonstrated that effectiveness of the natural enemies can be parti - then , this mealybug has been seen only rarely . Over the years , this effort has saved the California or completely eliminated by the use of nonse - ally lective pesticides a prodigious amount for the mere or by honeydew - seeking ants . citrus industry cost of $ 1,700expenses plus Compereâ??s salary of Lately , the woolly whitefly has been brought $ 50 per month . under complete biological control wherever it has Cales noacki Howard , Black scale was the most important citrus pest spread . The parasites imported from Chile in 1970 , and Amitus spin - Metaphycus helvolus up to about 1940 . In 1937 , @ i ( Brethes ) , from Mexico and other countries Compere was imported from South Africa , cultured , and released in numbers . It built up and during 1967 - 70 , are responsible for this most spread rapidly , especiallyin coastal areas . Since recent great success . 1940 - 41black scale has continued to decrease Also , during the last decade , the invading and everywhere , so that today it is , at most , an occa - potentially serious Comstock mealybug has been sional minor pest . brought under complete biological control in the The California red scale assumed primary pest San Joaquin Valley , principally by the impo & d status following the reduction of black scale . It Japanese parasites Allotropa burrelli Muesebeck had been the object of biological control research Pseudaphym rnulinus Gahan . and Since 1978the bayberry whitefly has invaded since 1890 , with no significant results , although a southern Californiaand spread on citrus . Already , Comperiella bzjimciata Howard , natural enemy , Eretmo - two apparently new species of parasites - from China became well established . Just after II , ecologicalfield studies demonstrated World War c i sp . and Encarsia sp . - have been established that Aphytis chqsmphali Mercet , a naturally from collectionsmade in Japan between 1979and established parasite , was effective in some groves are known and 1981 . Other exotic parasite species in strictly coastal areas . This led to a search for will be imported . Some study groves have already Aphytis . new and better species of shown complete control by the parasites in 1982 , be but the ultimate degree of successremains to Aphytis lingnanensis Compere , imported in seen . 1947from southern China , became generally For control of another pest , the brown garden untreated establishedand was quite effective in snail , Riverside researchers have found and intro - groves in coastal and intermediate areas . Aphytis Ruminia decollata . duced the predatory snail DeBach , imported from India and melinus Research on biologicalcontrol of citrus pests will A . Pakistan in 1956 - 57 , generally supplanted continue to emphasize discovery and importation lirgnamis in intermediate and interior areas , of new natural enemies and investigation of new where its effectiveness in untreated groves ranges research approaches . from moderate to complete depending on local Cmperiella bi & . sciata severity of climate . Integrated pest management ( Chineserace ) and Encarsia ( = Prospaltella ) per - niciosi ( Tower ) complement the Aphytis spp . the last few years , research on integrated During Thus , biological control of red scale is substantial , pest management ( IPM ) has resulted in a practical areas ranging from essentially complete in some program for citrus in southern Californiacoastal to ( Ventura County ) to inconsequential ( desert areas U.S . Department of inland zones . Studies at the and the San Joaquin Valley ) . The search for better Agriculture Boyden Laboratory have developed adapted parasites continues . pheromone techniques for use in trapping male The yellow scale was once a major pest of citrus , Californiared scale and mealybugs to detect and and thousands of acres were treated annually . monitor infestations . An important result shows Cmperiella bzjimciata After colonization of that the number of red scale males trapped is a Howard ( Japanese race ) from Japan in 1931 , sensitive indicator of the threshold above which yellow scale populations were rapidly reduced in is likely to occur . economicdamage to the crop southern California and later in the San Joaquin Future research will focus on quantitative Valley . Today this scale is virtually never seen . biological data for each species in the pest The purple scale declined considerably following complexand for the natural enemies , and on Aphytis kpidosapha Compere the introduction of is envi - determinations of economicthresholds . It from south China in 1948 . Today it generally is sioned that , through multidisciplinary approaches controlled by this parasite . and teamwork , we will move toward the long - Many other insects are also held in check princi - range goal of integrating knowledge of citrus pests enemies , including the pally by imported natural use in choosing into a computer - assisted model for dictyospermum , chaff and oleander scales , the optimal field procedures . longtail and citrus mealybugsand the citrus whitefly . Other citrus pests are controlled com - or at certain times and places by naturally pletely occurring natural enemies . These include the CR - 15