Annual Reports

1995—UC IPM Competitive Grants Program

Biorational Use of Biotic Agents

This category includes development and evaluation of methods of applying or using biotic agents or regulated pest control materials more effectively and in an environmentally sound manner. Examples might include efficient production and quality control of biotic agents; application or delivery technology, effective application and use of pheromones, attractants or repellents; methods of reducing the impact of pesticides on beneficial organisms, and methods of improving the safety, reducing environmental contamination or reducing the total amount of the control agent needed for effective control. Research on biotic agents may include the development of technologies to maintain their survival and/or residual activity and to effectively deliver them to target sites.

Research on the development and testing of environmentally safe chemicals will be considered if ongoing research has shown that no reasonable alternatives exist and that there is a good potential for their use. If the proposal involves an unregistered chemical, microorganism, etc., the mechanism and time frame for pursuing registration must be detailed. Highest priority will be given to research that involves materials that are environmentally benign.

If the proposal involves the eventual registration of a pesticide, modified microorganism, etc., the Pl must indicate how and when registration data will be obtained. It must be made clear whether registration will delay use of the product in the field.

New Projects Funded for 1995-96

Can Honeydew Management Increase Parasite Effectiveness?

The role of honeydew or nectar in the biological control of armored scales by Aphytis melinus in San Joaquin Valley citrus groves. (Year 1 of 2; $15,363)

Principal Investigator: R. F. Luck, Entomology, Riverside

Objectives:

Identify the sources of carbohydrates likely to be encountered by Aphytis melinus in a San Joaquin Valley citrus grove.

Determine whether Aphytis actually feeds on these carbohydrate sources in the field.

Determine the frequency with which groves, and trees within groves, have carbohydrate on their leaves, quantify its availability, identify the source, and determine how it varies seasonally.

Determine whether the application of carbohydrates in a grove will increase the Aphytis populations and decrease California red scale or yellow scale. populations.

Establishment and evaluation of a biological control program against the eucalyptus snout beetle, Gonipterus scutellatus Gyll. (Year 1 of 2; $28,697)

Principal Investigators: L. M. Hanks, Entomology, Riverside; T. D. Paine, Entomology, Riverside; J. G. Millar, Entomology, Riverside

Objectives:

Determine the current distribution of the eucalyptus snout beetle (ESB) in southern California and monitor its spread and rate of increase.

Optimize conditions for rearing and propagating a natural enemy of ESB, the egg parasitoid Anaphes nitens.

Conduct field releases of A. nitens, and monitor establishment.

Evaluate the efficiency of A. nitens in controlling populations of ESB, and its impact on damage to eucalyptus caused by ESB.

Cultural approaches to control brown rot of stone fruits in California. (Year 1 of 2; $21,380)

Principal Investigator: T. J. Michailides, Plant Pathology, Davis

Objectives:

Determine the importance of Monilinia fructicola apothecia as a source of primary inoculum in stone fruit orchards in the San Joaquin Valley.

Study the conditions that favor the stromatization of mummified fruit by Monilinia fructicola, which enhances the production of apothecia capable of initiating blossom infections in the spring.

Determine the importance of thinned fruit as a source of inoculum during the season, and whether thinned fruit can become stromatized, overwinter, and produce apothecia in the spring.

Field test of more effective traps for the walnut husk fly. (Year 1 of 2; $10,500)

Principal Investigators: C. Pickel, UC IPM Project, Sacramento Valley; S. Opp, Biological Sciences, California State University, Hayward

Objectives:

Field test in three commercial walnut orchards, two different trap designs and three lures, for development of a walnut husk fly trap which will better indicate population levels and onset of egglaying necessary for monitoring and timing of sprays.

Determine the effects of trap height in trees for optimal walnut husk fly detection in early season and in low fly density orchards.

Continuing Projects Funded for 1995-96

Managing Peach Yellow Leafroll

Evaluation of control practices for peach yellow leafroll disease. (Year 2 of 3; $20,760)

Principal Investigator: B. Kirkpatrick, Plant Pathology, Davis

Objectives:

Determine if premature defoliation or late season insecticide applications can decrease the incidence of peach yellow leafroll (PYLR) disease in four high risk peach orchards located in Northern California.

Determine what effect, if any, zinc sulfate mediated defoliation has on peach yields under Northern California growing conditions.

Monitor and determine the infectivity of mycoplasma-like organism (MLO) insect vectors caught in yellow sticky traps placed in the four high risk orchards.

Determine what PYLR-MLO strains are causing new infections in the 4 test orchards and other orchards that are currently using pheromone disruption practices.

In 1994 it was shown that blossom set and fruit yields on trees prematurely defoliated with zinc sulfate in October, 1993 were indistinguishable from untreated controls. This result suggests there is no immediate deleterious effects associated with fall applications of zinc. However, it will be necessary to repeat these treatments on the same trees to insure that there are no potential cumulative effects associated with zinc-mediated defoliation.

In 1993 and 1994 we mapped the locations of PYLR-infected peach trees in four high risk, northern California orchards and established randomized blocks of the following four spray treatments in each test orchard: water control, zinc sulfate-mediated defoliation, pyrethrin (Asana) insecticide only, and zinc with insecticide. All materials were applied by grower cooperators using a conventional airblast orchard sprayer during the first week of November, 1994. The efficacy of these treatments will be established by determining the number of new PYLR infections in each treatment block in 1995. Samples will be taken from newly infected PYLR trees and the type of MLO causing the new strike will be determined. In this manner we will establish whether any of our treatments are effective in reducing PYLR tree losses.

Projects that Ended in 1994-95

Traps for Walnut Husk Fly

Development of more efficacious and selective attractants and traps for the walnut husk fly.

Principal Investigators: C. Pickel, UC IPM Project, Sutter-Yuba Counties; S. Opp, Biological Sciences, CSU Hayward; S. Kint, D. Light and R. Teranishi, USDA, ARS, Albany

Objectives:

Quantify the release rate of ammonia from commercially available walnut husk fly (WHF) lures, from our laboratory-developed slow release ammonia dispensers, and from Nulure bait at various pH's, and determine the optimal release rate of ammonia needed to attract and capture WHF.

Collect, identify and assay the major components of walnut husk volatiles to determine relative attractiveness of these components to male and female WHF.

Determine sex, age, feeding status, and mating status of WHF attracted to traps baited with ammonia and/or walnut husk volatiles.

Cooperate with UC. Farm Advisors to test the efficacy of our ammonia-baited traps and our walnut volatile-baited traps for damage predictions and timing of pesticide applications.

Using laboratory-released marked WHF, we demonstrated that the most attractive ammonia-based lures are also non-selective lures, capturing WHF of different sex, age, and feeding history equally, regardless of the type of trap used. On the other hand, when walnut volatiles are used as the lures, whether on yellow panel or green sphere sticky traps, the traps become selective for male WHF, although the numbers of flies captured are far smaller than on ammonia-baited traps. Trap captures of the marked flies very closely mimicked the capture patterns of wild flies in the walnut orchards indicating that our marked flies were good predictors of wild fly behavior in the field.

Delays averaging three to ten days occurred following marked fly releases before these flies were captured on traps. Older flies (reproductively mature) were captured significantly sooner than younger flies, and the green sphere traps baited with ammonium carbonate captured the released flies most quickly. We also found evidence that traps placed high in the tree canopy are more effective at capturing flies than traps lower in the trees.

Indications are that both ammonia and walnut volatile baited traps, whether yellow panel or green sphere, can play important roles in WHF monitoring and pesticide application decisions. Walnut volatiles are more selective lures and may give better indications of the onset of egglaying so that growers can make more informed decisions about when to begin pesticide applications. Ammonia lures likely provide better estimates of the severity of WHF infestations.

Principal Investigators: L. Harshman, Entomology, Davis; M. P. Parrella, Entomology, Davis

Objectives:

Evaluate juvenile hormone analogs (juvenoids) for control of Bemisia tabaci.

Determine compatibility of natural enemies of B. tabaci with selected juvenoids.

Principal Investigators: C. Pickel, UC IPM Project, Sutter-Yuba Counties; S. Opp, Biological Sciences, CSU Hayward

Objectives:

Assess walnut husk monoterpenes and sesquiterpenes, individually and in combinations, for attractiveness to walnut husk flies at the key phenological time when female oviposition damage occurs in walnut orchards.

Correlate attractiveness of walnut husk volatiles plus ammonia on yellow panel and green sphere traps with onset of oviposition damage in walnut orchards to develop a predictive trap for timing control measures.

Summary of Progress: Volatile chemical odor components of walnut leaves and husks were tested individually and in multiple-component blends for attractiveness to male and female walnut husk flies in the field. Fifteen chemicals were presented on rubber septa hung from yellow sticky panel traps in walnut trees. Trees were located in an unsprayed walnut orchard (Payne variety) in Newark, California and in a commercial orchard (Hartley variety) in Modesto, California. In Modesto, heavy insecticide spraying by the grower to diminish husk fly damage forced us to stop this test after collecting three weeks of data. Data from 8 weeks of testing in Newark indicated that male walnut husk flies show differential attraction to the various walnut odors and that one chemical, caryophyllene, is the most attractive single chemical. Female flies showed little attraction to any of the odor components. Attraction of flies to the lures was very low in early season (prior to onset of female egglaying) and in late season (after most walnuts were already damaged). Trap captures of males dramatically increased in Newark as female egglaying became apparent, but the exact date of onset of first female egglaying was not pinpointed. Because increased male attraction to particular walnut volatiles, especially the commercially available caryophyllene, appears to coincide with onset of female egglaying, we feel there is a strong possibility of developing a selective male trap which would lead to more accurate timing of insecticide sprays to control walnut husk fly.

Final Reports for Projects that Ended in 1994

Parasite Releases for Red Scale

An evaluation of augmentative releases of Aphytis melinus as a control tactic for California red scale in San Joaquin Valley citrus.

Principal Investigator: R. F. Luck, Entomology, Riverside

Summary of Accomplishments: Previous research (UC IPM Publication 15) suggested that augmentative releases of Aphytis melinus suppressed red scale in San Joaquin Valley citrus when they are part of a comprehensive pest management program. This program includes: (1) conservation of natural enemies, (2) monitoring of the five major citrus pests, (3) the use of intervention thresholds, (4) selective pesticides or other control tactics that minimally disrupt natural enemy populations (e.g., a high-pressure post-harvest washer for armored scale and sooty mold) and, (5) releases of 5200 Aphytis per acre every two weeks from about 15 February until 15 November (= 100,000 wasps per acre per year). This pest management program produced fruit that were equal to or better in quality at a cost equal to or less than that incurred with the traditional, chemically-based program.

The experiments we conducted under the auspices of the UC IPM program sought to document the efficacy of augmentative Aphytis melinus releases as part of this pest management program. Preliminary results in the San Joaquin Valley indicate that the released Aphytis coupled with the resident natural enemies provided economic suppression of the armored scale. About 60 to 80% of the scale on the leaves and 40% of the scale on fruit died from either plant or climate effects and the remainder died from natural enemies. Aphytis is a major source of mortality in those scale killed by natural enemies. It acts as both a predator of small scale, which it kills by host-feeding, and a parasitoid of older scales, which it kills by parasitization. Without the mortality from natural enemies, the scale populations would have increased seven-fold or more each generation.

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