Barnett, William W. : William W. Barnett is Area Specialist, Cooperative Extension, Fresno County

Bentley, Walter Joseph

Cahn, Daniel : Daniel Cahn are Staff Research Associates, U.C., Berkeley

Castro, Darryl : Darryl Castro and Daniel Cahn are Staff Research Associates, U.C., Berkeley

Coviello Mr, Richard L.

Hendricks Mr, Lonnie C.

Hoy, Marjorie A. : Marjorie A. Hoy is Associate Professor and Entomologist, Department of Entomological Sciences, University of California, Berkeley

Reil, Wilbur O. : Wilbur O. Reil is Staff Research Associate, U.C., Davis

Large - scale releases of pesticide - resistant spider mite predators Marjorie A . Hoy 0 William W . Barnett Wilbur 0 . Reil Darryl Castro 0 Daniel Cahn 0 Richard Coviello 0 Walter J . Bentley Lonnie C . Hendricks Research also showedfor thefirst time that mitepredators â?? planted â?쳌 in almond orchards can disperse aerially . son ; document their ability to overwinter ; the greenhouse system , but large numbers of Spider mites can be seriouspests in Califor - and determine if pesticide rates can be re - predators were not available for release until nia almond orchards . In some orchards , the duced to manage spider mites and predators . early August . The soybeans were planted Metaseiulus ( = Typhlodromus ) occi - mite April This report describes our progress in rearing 27 , and 31 flats of spider mites and car - dentalis ( Nesbitt ) is an effective predator of the Pacific and two - spotted spider mites , large numbers of the resistant predators , their baryl - OP - resistant predators were added on Tetranychus pacrfcus McGregor and T . ur - a previously unknown M . oc - establishment , and four occasions in June . Total input of cidentalis ticae Koch , respectively . Pesticides used to phenomenon - large - scale aerial dispersal of was estimated to be 180,000 M . occidentalis from an almond orchard . control the navel orangeworm , AmyeIois females . By August , the plants were about 4 feet tall transitella ( Walker ) , and the peach twig Predator rearing and could be harvested . Leaf samples taken Anarsia lineatella Zell . , can disrupt borer , on August 6 indicated that the half - acre plot this biological control , however . Carbaryl Two systems were developed to produce 32 million M . oc - contained approximately ( Sevin ) and the new pyrethroid permethrin predators . Most of the 1.5 million M . occi - cidentalis females , plus at least another 30 ( Ambush or Pounce ) can causeseriousspider dentalis females released in almond orchards million immatures and males . Each soybean mite outbreaks by killing spider mite preda - during 1981were reared on pinto beans , Pha - 300 predator plant contained an average of tors , including M . occidentalis , by stimu - seolus vulgaris ( L ) , in a University of Califor - females . lating spider mite reproduction , or by causing nia , Berkeley , greenhouse . Plants were This method was the least expensive in pro - dispersal of spider mites , which also can en - grown in flats containing one - half U.C . soil ducing large quantities of predators in in - hance their reproduction . mix and one - half vermiculite . In the initial oculative releases during August or Septem - M . occidentalis has been selected in the phase of greenhouseproduction ( February to ber for largeacreages . Control of spidermites laboratory for resistance to carbaryl and to May ) T . urticae were added to the bean plants cannot be expected during the field season of permethrin ( CaliforniaAgriculture , January as soon as dicotyledon leaves appeared . release with these late releases . However , this 1980 and November - December 1980 ) as part About one week later , resistant M . occiden - procedure should be helpful in establishing a of a genetic improvement project . The two talis were added . Plants were treated with population that will be effectivethe following strains , which are also resistant to organo - carbaryl or permethrin periodically to ensure year . phosphorus insecticides , such as Guthion that the predator colonies remained resistant ( azinphosmethyl ) , diazinon , and Imidan and that nonresistant predators were re - Predator releases moved . Each strain was maintained on ( phosmet ) , are called carbaryl - OP and per - methrin - OP resistant . These strains have separate benches in the greenhouse . In all cases , both predator strains were been evaluatedin the laboratory , greenhouse , Low rates of acaricide ( Omite 30 WP , ! h released in the orchard after the relevant and small field plots to determinetheir ability to Yi pound per 100 gallons water ) were ap - so that native insecticide had been applied to become established , control spider mites , plied when predator - prey densities became ( susceptible ) predators were largely elimi - overwinter in orchards , and survivecommer - nated . Pinto bean plants were cut and placed 40 to 50 imbalanced ( usually more than cial pesticide applications . spidermites of all stagesto 1predator ) . After in the crotch of the tree . Releasepatterns and of genetic improvement of The concept the predator - prey system stabilized in May , numbers released varied from orchard to or - biological control agents previously received chard ( see table ) , but most often 350females predators were multiplied by cutting old little support because of concerns that labor - plants containing both spider mites and were placed in every third tree , in every third M . atory - selected natural enemies might not be occidentalisand placing them on clean young row . Unknown numbers of males and imma - as effectiveas unselected â?? wild â?쳌 strains . Be - tures were released as well . bean flats . These divisions yielded three new cause our previous field plots were small and We expected establishment in the tree and flats everytwo to three weeks during the sum - not always managed â?? normally â?쳌 by the mer . Continuous production of predators spread from release trees to adjacent nonre - grower , we conducted research on the feasi - lease trees sometimeduring the 1981field sea - from June to September was possible , and bility of large - scale field releases of pesticide - about one million carbaryl - OP - resistant son . Releases were made throughout the resistant strains of predators for spider mite 227,000 permethrin - predator females and summer when adequate prey were available OP - resistant females were released . control . Goals were to rear resistant M . oc - a minimal to support the predators ; that is , cidentalis and release them in San Joaquin Predators also were reared outdoors in a prey level of one - half to one spider mite of half - acre soybean plot in the San Joaquin Valley commercial almond orchards ; docu - any stage per leaf . Black cotton cloth bands Valley . This method required less labor than ment their establishmentduring the first sea - were stapled to major scaffolding limbs of 8 CALIFORNIA AGRICULTURE , JANUARY - FEBRUARY 1982 release and nonrelease trees in all orchards during September . Overwinteringfemalepre - dators recovered from the bands during De - cember and January will be tested in the laboratory to determine if they are resistant and well distributed in the release orchards . Spider mite populations were managed by using low rates of Omite ( Yi , 1 , or 2 pounds 30WPper acre ) or Plictran ( Yi or 1 pound per acre ) both before and after predators were re - leased . Use of these low rates sometimes gave poorer spider mite control than desirable if M . occidentalis were not ade - populations of quate or well distributed in the orchard . Weather , population densities , and irrigation schedulesare also important in determiningif these low rates give satisfactory control . If the weather is extremelyhot , spidermite web - bing has built up , or the orchard is water stressed , low rates of Omite or Plictran may Above : Mite predators not control spider mites sufficiently to pre - were released In or - chard at rlght but not vent foliage damage . Thus , although low in defoliated trees . of these selective acaricides are poten - rates tially useful in spider mite management , con - siderable experience and monitoring are re - quired to prevent excessive damage from spi - der mites . We will continue to evaluate such use of 1982 , because low rates can acaricides during prevent predator - prey imbalances resulting of food , reduce grower from temporary loss Left : Spider mitewebs costs , and retard development of resistance indicate severe dam - to these chemicals . Selection for dominant age in almond trees . resistancegenes will be slower in nativespider mite populations if acaricides are used infre - Below : Researchers quently and at low rates . Plictran resistance check soybean nur - sery fieldwhere 62mil . has been found recently in spider mites in llon predators were Oregon pear orchards ( P . H . Westigard , rearedfor releaseinal - personal communication ) and serves as a mond orchards . warning of the potentiallylimitedlife span of these acaricides in California . Aerial dispersal We suspected that carbaryl - OP - resistant M . occidental & dispersed aerially in the Bidart almond orchard near Bakersfield dur - ing 1979 - 80 . A few predators had been re - 1979at one end of the block , leased in August and by August 1980 the carbaryl - OP - resist - ant predators were present throughout the l ) , which indi - block in large numbers ( fig . cated they had established , spread , and sur - vived a carbaryl application in July 1980 . An additional sample and laboratory test with carbaryl in April 1981 showed that the resis - tant strain had survived a second winter . so widely distri - Because the predators were buted over at least 50 acres , aerial dispersal was suspected . 1981 , we conducted an experimentto de - In termine if our suspicion was justified . Car - baryl - OP - resistant M.occidentalis were re - on June 9 into every third tree , every leased CALIFORNIA AGRICULTURE , JANUARY - FEBRUARY 1982 9 Almndr corboryl - OP resistant sistant predators will disperse from the 01 " release sites , - 1981 or how to manage the resistance . Almonds o - 1980 in the orchards or vineyards to which the re - field crop3 sistant M . occidentatis disperse . permethrin - OP resistant 210 During 1980 and 1981 , we inoculated 1 A A A A - 1981 and 86 acres of almonds in the San Joaquin N A A - A - 1980 Valley with the carbaryl - OP - and permeth - t \ \ 2 ) . rin - OP - resistant strains , respectively ( fig . I u \ It will be interesting to learn whether these in * ' \ orchards will serve as foci for the spread of Almonds carbaryl resistance ( determined by a single major semidominant gene ) into other orchards or vineyards . ( Spread of the per - methrin - OP - resistant strain is not expected , because permethrin resistance is determined by several genes . If this strain interbreeds ex - tensively with permethrin - susceptible wild Fig . 2 . Dispersal of two resistant Fig . 1 . Carbaryl - OP - resistant M . occidentalis predators , the resistance is lost . ) Only careful M . occidentalis strains from almond were released in 80 - acreorchard , 1979 . Resis - monitoring of the area around these release orchards where releases were made tant predators were recovered in 1980 and sites can resolve our questions . It is clear for in 1980 and 1981 . 1981 , indicating extensive movement . the first time , however , that M . occidentalis can disperse through the air . The relative im - third row , in an almond orchard ( Livingston - Six plastic panels , 9 by 12 inches , were levee . I in table ) . Carbaryl had been applied in May portance of this method of dispersal remains coated with high vacuum grease ( Dow Corn - and again on July 3 . Despiteapplications of 2 ing ) and attached at three levels on the tower . to be resolved . pounds 30 WP'Omite per acre on July 3 and After removal from the orchard , the panels 21 , spider mites increased and caused sub - were scanned with a dissecting microscope , Marjorie A . Hoy is Associate Professor and Entomologist , Department of Entomological stantial foliage damage and some defoliation and spider mite and predator numbers were Sciences , University of California , Berkeley ; because populations were high when the estimated by counting one - ninth of the panel William W.Barnett isArea Specialist , Cooperative acaricide was applied . The abundant spider Extension , Fresno County ; Wilbur slide - 0 . Reil is Staff area . Predators from the panels were Research Associate , U.C . , Davis ; Darryl Castro mites also provided unlimited food for the mounted and identified to species ; all were and Daniel Cahn are Staff Research Associates , predators , which multiplied extensively . M . occidentalis females . No immatures or U , C , , Berkeley ; Lonnie C . Hendricks , Richard J . Bentley are FarmAdvisors , Coviello , and Walter As foliage quality declined , spider mites males were recovered on the panels . CooperativeExtension , Merced , Fresno , and Kern M . occidentalis in the Aerial dispersal of T . urticae and T . pacifcus ( predominantly counties , respectively . We thank K . Casanave , E . field has not been documented previously . females ) began to disperse from the orchard Serber , D . Ravetto , T . Browne , and R . Griggfor assistance . This project is supported in part by The dispersal raises interesting questions in July . Dispersal was detected by trapping fundsfrom the Almond Board of California , IPM about the fate of the resistant strains we have the mites on sticky panels situated on two Program of the CaliforniaDepartment of Food released . We know how to establish resistant towers placed at the east end ( downwind of and Agriculture , and Experiment Station Project 3522 - H . We are especially grateful to the growers predators in specific orchards after the rele - prevailing winds ) of the orchard on July 31 . who made their orchards available : Bidart Farms , 25 feet vant pesticidehas been applied . However , we The 11 - foot - high towers were about Blackwell Land Company , C.V . Horton , A . Bet - tencourt , Sumner - PeckRanch , and H . Deniz . from the edge of the orchard on a 2 - foot don't know how rapidly or how far these re - 10 CALIFORNIA AGRICULTURE , JANUARY - FEBRUARY1982