Flaherty, Donald L. : Donald L. Flaherty is Farm Advisor, Tulare County

Jones, Richard A

Rice, Richard

Monitoring and modeling San Jose scale Richard E . Rice Donald L . Flaherty Richard A . Jones s a n Jose scale , Quadraspidiotuspernicio - knowledge of San Jose scale behavior that sus ( Comstock ) , is one of the worldâ??s most should lead to improved control strategies severe pests of deciduous fruits and nuts . and management of this pest , particularly in This insect arrived in the United States from situations where dormant sprays have not 1870 and was first re - the Orient in about of the been used . This report presents some ported damaging fruit trees in California in new techniquesand discusseshow they can be 1873 . Although several parasites and preda - used to develop pest management programs tors attack San Jose scale ( SJS ) , economic in deciduous orchards . control has depended on insecticides.Chemi - 1973 the presence of a sex pheromone in In cal controls usually include dormant sprays San Jose scale was confirmed ; researchers at of organophosphate insecticidesand / or nar - Cornell University identified and synthesized the pheromone in row - range oils , or foliar sprays directed 1977 - 78 . With the availabil - of a synthetic pheromone , techniques for against immature ( crawler and white cap ) ity San Jose scale infestationsas extensive as stages in the spring and early summer . monitoring scale populations were soon de - this one on almondtwigcauselargelossesof of dormant treatments is usually Timing veloped for field use . The Zoecon SJS â?? tent â?쳌 bud and fruit wood and cullingof fruit.Above not too difficult ; timing of sprays for crawler trap used for San Jose scale is different from right , adult male hascharacteristicblack bar activity has sometimesbeen inaccurate . In re - those used for Lepidoptera species but has a across thorax , long antennae in relation to ( 10x1 cent years advances have been made in our body , and small head and eyes . rubber dispenser ( cap ) similarto other phero - mone dispensers . For routine monitoring , tent traps are placed about 6 to 7 feet high in the north or east sidesof host trees . They must be securely fastened with a wire hanger to a tree limb to of the prevent them from being blown out tree by the wind . At least three traps should be used for monitoring San Jose scale , re - gardless of orchard size . In orchards larger than 30 acres , one trap per 20 acres is recom - mended . Traps should be inspectedtwice weekly for male scale and cleaned , particularly in early March when collection of first males is im - portant in using the scalephenology model to time subsequent crawler emergence . Traps should be replaced whenever they become too dirty for accurate identification and counting of male scale ; pheromone caps should be replaced every six weeks . Care must be taken to correctlyidentify male scale collected because of their small size . With this trapping system , male San Jose scale flights and population trends can be monitored relativelywell ( seegraph ) . For de - tection of scale infestations in deciduous or - chards , the traps offer an early - warning CALIFORNIA AGRICULTURE , JANUARY - FEBRUARY1982 13 Day - degreerequirements for development of life stages of San Jose scale * Fi.eld data indicatethat natural populations Day - degrees of the two - spotted spider mite , Tetranychus Stage Male Female urticae Koch , can decrease strawberry yields When we evaluated a so - called mid - curve , by 10 to 15 percent at various harvest periods Embryo ( egg ) development 405 421 in which all stages ( black caps , mature 1964 , entomologists during the season . Since mated , and unmated females ) of San Jose at University of California , Riverside , have First instar scale would be expected to survivethe winter been conducting research to develop a prac - ( crawlers , white caps , and produce individualsin the spring genera - 318 331 black caps ) tical program for managing the mite on tion , we found a much closer correlation summer - and winter - planted strawberries in Second instar 213 220 between observed events and what the model of southern California , studyingthe efficacy projected should happen . This was true for predatory mites and selective miticides , as Pupal stages - males 95 both time periods : from January 1 until first well as the injury caused by spider mite Tight cap - females 58 males were trapped , and from first males Feeding . Effectivecontrol measures are being Pre - matingadults 19 20 trapped until first crawlers were observed . sought for incorporation into integrated pro - When the third hypothetical generation or yams in commercial strawberry plantings . Average DOIgeneration 1050 1050 growth curve was evaluated , in which only * Lower threshold = 51 F ; upper threshold = 90 ' F . The Photosynthesisand productivity overwintered mature females would be ex - lower threshold is the temperature below which the insect's development stops ; the upper threshold the temperature pected to survive , we again found consider - In California , commercial strawberry vari - above which the development rate begins to decrease . The amount of heat between the two thresholds that is needed able variation between observed events in the eties produce fruit continuously throughout for the insect to develop from one stage to the next is field and those the model projected , particu - the winter and spring . Fruit filling and calculated in daydegrees - the degrees of temperature above a threshold for each day . Doaccumulationsfrom first males larlyin the enlargement occurs when plant canopies are until first crawlers appeared in the field . established and after the plant's initial stor - alternative to laborious inspection of fruit From a practical standpoint for California , age reserves have been utilized . Carbohy - the early or mid - curves would be the most drates and other materials migrating into or the even less desirable method of wood finding infested fruit . After the pheromone realistic with regard to scale development . developing berriesoriginatepredominantlyin trapping system for San Jose scale was in - In considering how the San Jose scale chlorophyllous tissues , and the relativequan - troduced , research cooperators in Utah and of nutrients available primarily depends model can be used in pest management pro - tity on the rate of photosynthesis , in which sugars Michigan produced a phenology model for grams , application of chemical controls for ( photosynthates ) are produced by the bind - scale , using a large amount of California scale crawlers in May would be one of the ing data . Early - season ( first - flight ) trapping of carbon and water molecules into most critical areas to evaluate . Based on carbon - based chains . Photosynthesis occurs model projections , we would anticipate data used in conjunction with the model within the chloroplasts of leaf cells and is should lead to improvedtiming crawler emergence approximately of treatments 400 Do powered by solar energyabsorbed by the pig - after the first males in any given generation for San Jose scale , particularly against ment chlorophyll . The required water is crawlers in late April or early May . Using have been collected in pheromone traps . As brought up from the roots through the pro - in the case with oriental fruit moth egg hatch , of 51 O and lower and upper threshold values of translocation . The second compon - cess however , we suspect that spray timings at the 90O F , respectively , the day - degree require - ent , carbon dioxide , enters the leaf tissue of crawler emergence prob - very beginning ments as used in the model are given in the through the stomata - small closable aper - ably would not be optimum , but instead table . tures in the epidermis . While stomata facili - The model accommodates three hypothe - should be delayed for several days . This tate movement of carbon dioxide into the means that we could add approximately tical types of growth curves for San Jose 100 leaf , they also allow large quantities of water scale . In the first cycle or generation curve to 150 Doto the crawler emergence curve to be lost by evaporation to the atmosphere - that we might expect to see for San Jose scale , beyond first crawler and spray at that point . a process known as transpiration . When This approach to spraytiming for San Jose only overwintered black caps ( late first - stage transpiration rates exceed the rate of water scale ) would be producing new crawlersin the scaleneeds to be verified with field plot work . uptake by the roots , the plant wilts . However , as in the case with the oriental fruit spring . This is the so - called early curve . Photosynthates are required for respira - 225 moth model , we still feel that the model is Calculations show that , on the average , of vegetative structures tion and growth sufficiently accurate to begin using it under a Dowere required for scaledevelopmentfrom ( leaves , stems and roots ) as well as for fruit variety of pest control advisorand grower ap - January 1 to the point at which first males production . By continuously producing new plications to challenge its validity and detect were observed in pheromone traps , with an foliage , the plant replacesleaves that may die early population curve . However , the model the weak points that undoubtedly exist . within several weeks after development . 274 Do are required , on the projects that Feeding by two - spotted spider mite causes average . Similarly , development from first Richard E . Rice , Entomologist , Department of plant stress , which detrimentally affects male flight in the spring until first crawlers Entomology , Davis , is located at the San Joaquin photosynthesis , transpiration , fruit produc - 323 were observed required approximately ValleyResearch Center , Parlier ; Donald L . Flaherty is Farm Advisor , Tulare County ; and Richard A . tion , and vegetative growth . Reductions in D O . The model projects a day - degreerequire - of Jones , Staff Research AssociateIV , Department photosynthesisrates from mite - caused stress of 372 " . Therefore , in the hypothetical ment Entomology , is located at Parlier . Appreciation is decrease berry production ( fig . 1 ) . The early curve we see a rather wide divergence expressed to the many CooperativeExtensionper - sonnel who have assisted in developing scale of stress and time of the season when amount between observed events ( first male , first trapping data and techniques over the past few stress occurs largely determine the extent of crawler ) and what the model predicts for years . This research was supported in part by injury to the strawberry plant . Ideally , grantsfrom the California Tree Fruit Agreement . these same events . 14 CALIFORNIAGRICULTURE , JANUARY - FEBRUARY 1982