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Annual Reports1996—UC IPM Competitive Grants Program
Biological ControlsBiological control is narrowly defined here as the use of predators, parasites, pathogens, competitors, or antagonists to control a pest. Efforts of the UC IPM Project should address those problems that have a reasonable chance of implementation within three years. An area of special interest for IPM funding is work to establish effective biological control in field situations. The Project would support studies of indigenous or introduced biological control agents to determine their efficacy, how they can be manipulated by cultural or other management practices to improve their efficacy, and how they are affected by pesticides. The Project would support development of methods for growers and PCAs to use in evaluating potential effectiveness of existing biological control agents in relation to pest populations and potential crop damage. Proposals must include a description of how proposed practices could fit into the current production or management systems. If current management practices must be altered to ensure the successful adoption of the research, these changes should be outlined. Proposals must be designed to produce practical guidelines, tools, and/or methods by the end of the project. Investigators should detail mechanisms for transferring methods or tools to field use.
New Projects Funded for 1996-97 Continuing Projects Funded for 1996-97 Projects that Ended in 1995-96 Final Reports for Projects that Ended in 1995
New Biological Control Projects Funded For 1996-97 BIOLOGICAL CONTROL OF NAVEL ORANGEWORM
SPOT TREATMENTS FOR ANTS Electronic spot spray applicator for ant management in orchards and vineyards. (Year 1 of 2; $18,930)
Principal Investigators: K. Giles, Biological and Agricultural Engineering, Davis; P.A. Phillips, UC IPM Project, Ventura County
Objectives: Develop an automatic, lightweight, ATV-mounted electronic system for spot spraying against honeydew foraging ants at the trunk/soil interface in tree crops and vines. Quantify the physical performance and ant control efficacy of the mechanical spot treatments with conventional hand sprays and band sprays.
ELECTROSTATIC DELIVERY OF BIOLOGICAL CONTROL AGENTS Precision, carrierless handling and placement of biocontrol organisms. (Year 1 of 1; $7,895)
Principal Investigator: K. Giles, Biological and Agricultural Engineering, Davis
Objectives: Determine the feasibility of "carrierless" handling, metering, and distribution of biocontrol organisms for field application; specifically, to evaluate the use of electrodynamic techniques for precision delivery and placement of the organisms. Determine if the biocontrol organisms can be electrically charged to useful charge/mass ratios. Determine the biological effects of electric fields on the viability of biocontrol organisms in the egg, larvae, and adult stages.
Continuing Projects Funded for 1996-97 WHITEFLY BIOCONTROL Enhancement of biological control of the silverleaf whitefly. (Year 3 of 3; $10,000)
Principal Investigators: T.M. Perring, Entomology, Riverside; T.S. Bellows, Entomology, Riverside
Objectives: Increase the diversity of natural enemies through importation, mass rearing, release, and establishment of exotic parasitoids.
Summary of Progress: In the first year of this 3-year study, we introduced a new parasite species, Amitus bennetti, into the Imperial Valley. This parasite is native to the Caribbean and we have observed aggressive parasitism of silverleaf whitefly by this species in both laboratory and greenhouse settings. Funding received from the UC IPM Project was combined with resources from the Imperial Valley Whitefly Management Committee, the California Cotton Pest Control Board, the California Melon Research Advisory Board, and the University of California Center for Pest Management. Our releases of A. bennetti continued through July 1995 and concluded with the release of 382,800 parasites distributed over 24 locations in urban and agricultural settings near Brawley and El Centro. A. bennetti adults were recovered from two urban sites, suggesting possible, but limited, establishment. Beginning in August 1995 we initiated release of Encarsia lutea, the second of three parasitoid species planned for release into the Imperial Valley. Thus far we have released 20,000 individuals and have also verified recoveries at 80% of the release sites. We believe that E. lutea will become widely established in the Imperial Valley and hopefully will add to the overall mortality of silverleaf whitefly populations in agricultural and urban settings.
Progress Reports for Biological Control Projects that Ended in 1995-96 APPLICATION OF PREDACEOUS MITES
Summary of Progress: A mechanical system for field distribution of commercial formulations of vermiculite carrier and Phytoseiulus persimilis predaceous mites was developed and field tested. The handling system consisted of an insulated storage reservoir, a rotating metering plate, and an air-cleared ejection port. Release rate of the mites was controlled through rotational speed of the metering plate and the size of cells on the plate. The release rate could be calibrated much like a conventional pesticide sprayer. Field testing found the system to uniformly release mobile mites with an average accuracy of 98% of the desired release rates from 32,000 to 92,000 predators/ha. A large scale test on 6.5 ha achieved a release rate within 5% of the target rate. In field comparisons between hand release and mechanical release, a four-bed mechanical distributor achieved a productivity of 2.1 ha per worker hour. An equivalent manual release achieved a productivity of approximately 0.26 acres per worker hour. Mechanical release provided an eight-fold increase in productivity but also required use of a tractor. The mite distributor has been adapted for distribution of green lacewing, Chrysoperla, eggs in vermiculite mixture. Laboratory results indicate that the distributor can uniformly release viable eggs. Vibration of the distributor at frequencies and accelerations measured on agricultural vehicles does not significantly reduce viability of eggs, as measured by hatch rates at various environmental conditions. The ruggedized distributor, constructed in 1995, has been loaned to cooperators and used for mite releases in strawberries and release of lacewing eggs in commercial vineyards. The design, evaluation, and performance information has been discussed in trade publications such as Farmer-to-Farmer, California Farmer, American Vegetable Grower, and the California Strawberry Advisory Board Pink Sheet. Design descriptions and release techniques have been provided to growers. A commercial manufacturer has adopted the design and produced a product based on the UC research.
NEW MICROBIALS FOR CATERPILLARS Field evaluation and implementation of selective microbial biopesticides in IPM programs.
Principal Investigator: B.A. Federici, Entomology, Davis
Objectives: Evaluation of a new nuclear polyhedrosis virus of the celery looper, Anagrapha falcifera, as a microbial pesticide for use in IPM programs against noctuid larvae. Evaluation of a new isolate of Bacillus thuringiensis subsp. kenyae as a microbial pesticide for use in IPM programs against the beet armyworm, Spodoptera exigua.
Summary of Progress: During the second (final) year of our project, we focused on a comparative field evaluation of different viral insecticides being developed for use in IPM programs to control noctuid pests. Our model system continues to be fresh market tomatoes, and the beet armyworm and celery looper viral insecticides. Though we are focusing on evaluations in tomatoes, the results we obtain in this system will provide guidance for evaluating these viruses against the same pests in other crop systems. The beet armyworm virus is very specific for the beet armyworm, whereas the celery looper virus is a "broad-spectrum" virus capable of controlling many noctuid pests. Based on previous trials, the beet armyworm virus would be the virus of choice in a situation where the beet armyworm is the major or only pest as it is more efficacious than the celery looper virus against the beet armyworm. In situations where the crop is being attacked by a complex of caterpillar pests (for example, the beet armyworm, tomato fruitworm, and loopers), the celery looper virus or a Bacillus thuringiensis (Bt) would be the microbial insecticide of choice due to their greater spectrum of activity. The virus formulations were produced and formulated in the laboratory at Riverside or by Biosys, Inc. (Columbia, MD), and then applied on tomatoes (Lycoperscion esculentum Mill.; Petoseed VFN 7718) weekly after first fruiting at the UC South Coast Field Station in Irvine, CA. Treatments were made from July 27 through September 14, 1995, after which tomatoes were harvested and evaluated for internal and external damage. Controls used in the trials included a standard chemical insecticide (Lannate), a Bt preparation, and untreated plants. In our second year trials, the celery looper virus continued to perform moderately well. At rates considered commercially acceptable, internal and external fruit damage totaled 8.25% in comparison to a damage rate of 21.25% in the untreated control plots. The beet armyworm virus applied at a similar rate was slightly better numerically, with a damage level at 7.4%, but analysis showed that this difference was not statistically significant. Damage in most Bt treated plots was about 8%, and in the plots treated with Lannate damage ranged from 2.5%. Neither the viruses nor the Bt products resulted in resurgence of leafminer populations, nor did they cause significant mortality to leafminer parasites. We consider these results quite promising, though improvement of another 50% in efficacy will probably be required to get these materials adopted by growers. Such an improvement should be obtainable by increasing the amount of virus applied, or through improvements of formulation technology currently underway in industry. Permission to market the beet armyworm virus in California during 1996 is currently being sought by Biosys (Columbia, MD), and they will soon be seeking similar permission from the California EPA to market the celery looper virus. Thus, growers will soon have the opportunity to evaluate these viruses under commercial growing conditions. We hope to help in determining just how to implement these new microbial insecticides in tomato IPM programs.
REDUCING CODLING MOTHS IN APPLES The potential of early season releases of Trichogramma platneri and sanitation practices to reduce codling moth in mating-disrupted apple orchards.
Principal Investigator: N.J. Mills, Biological Control, Berkeley
Objectives: Evaluate early season releases of Trichogramma platneri for the suppression of codling moth during its first generation in apple orchards under mating disruption. Compare the effectiveness of T. platneri in the two major climatic regions for apple growing, the north coastal region and the Central Valley. Evaluate the potential and timing for sanitation practices in reducing codling moth populations in apple orchards.
Summary of Progress: In this field season we set out to clarify how the number of parasitoid release points per plot might influence parasitism of sentinel eggs and codling moth damage in a mating disrupted apple orchard in the Central Valley. The release rate was held constant at 200,000 female T. platneri/acre for all treatment plots except the no-release control treatment, and the release treatments consisted of 13, 25, 50 or 100 release points per plot. An additional 50 release point treatment was included in which the parasitoids were provided with honey upon emergence in the field. The levels of sentinel egg parasitism and codling moth damage was compared between treatments. The results of the sentinel egg monitoring are difficult to interpret due to a large number of the eggs being eaten or damaged. Approximately half of the plots for each monitoring period had seven or less viable eggs out of the 15 sentinel eggs per plot. Combining the data from both monitoring periods indicated that the treatment of 50 parasitoid release points per plot had the highest parasitism (57%), while the other treatments, including the control, had parasitism of 10 to 13%. There was a trend of reduced damage with an increase in number of release points at both sample dates but the variability between plots was too great for this to be statistically significant. However, damage in the 50 release point plots was reduced by 20% in comparison to the 13 release point plots. Surprisingly, the 100 release point plots showed greater damage than the 50 release point plots, possibly as a result of handling the small pieces of card. Plots provisioned with honey at the parasitoid release points had no greater or lesser parasitism of sentinel eggs nor of codling moth damage than the equivalent plots with honey.
INTEGRATING PREDATOR RELEASE AND ACARICIDES Timing of predatory mite releases in strawberries and the effect of acaricides on the survival and establishment of Phytoseiulus persimilis Anthias-Henriot.
Principal Investigators: P. Phillips, UC IPM Project, Ventura County; J. Newman, UC Cooperative Extension, Ventura County
Objectives: Determine the relative effectiveness of three distinct predatory mite release methods: (a) hand releases with bean leaves, (b) hand releases with vermiculite bulk carry, and (c) machine releases with vermiculite bulk carrier. Examine the effect of four miticides (abamectin, dicofol, propargite and fenbutatin oxide) on the survival and establishment of introduced predatory mites in strawberry fields. Examine residual effects and feeding toxicity of these miticides in laboratory bioassays using field sprayed foliage and spider mites.
Summary of Progress: As a result of an unusually cold and wet winter, twospotted mites were very late in developing during the first year. Because of this delayed mite buildup at one of the test plots, our predaceous mite release timing strategy test was inconclusive. The "early" release treatment was made into extremely low and variable pest mite populations. The "no release" treatment was compromised when in late January, after a series of rains, one grower cooperator elected to make a predaceous mite release over the entire ranch. Ultimately, very little difference developed in mite levels between treatments or release timings. Nor were there any significant differences expressed in the yield portion of the study, as would be expected given no differences in pest mite levels. Because of a similarly delayed mite buildup at the other test plot, it was necessary to cut our originally planned and sampled replicates for the first set of applications from five to only three replicates, resulting in considerable variability and a less sensitive ANOVA analysis on treatment means. The grower was concerned about miticide applications adjacent to the local high school playing fields during the spring when students are active. His policy is no treatments this time of year, if at all possible, thus precluding the use of the two planned replicates adjacent to the school. For the second test, we were able to add only one additional replicate by cutting out two of the least efficacious miticides. This was still not sufficient to significantly increase the ANOVA analysis sensitivity for treatment means. Agrimek gave the best twospotted mite control of the miticide products tested while allowing survivorship of predator mites. Predator mite levels were lower in the Agrimek plots, but then so were the twospotted mite populations upon which they are obligate predators. However, there is also a confounding long-term residual effect on P. persimilis. In the second test, Agrimek appeared to give a better knock down on twospotted mites than Vendex on the first posttreatment sample, but this late in the season the pest mite levels were decreasing anyway. No significant differences between treatments were noted on any of the sample dates.
IMPROVING PARASITE APPLICATION METHODS
Determine the pattern of distribution of parasitized eggs within the tree canopy and the parasitoid emergence rate after broadcast application from the ground. Evaluate the effectiveness of T. platneri augmentation against codling moth in replicated field trials comparing broadcast and point source release. Demonstrate season-long control of codling moth using the most effective strategy for augmentative releases of T. platneri in several commercial walnut orchards. Summary of Progress: We have previously demonstrated that the extent of damage to walnuts by codling moth can be reduced by as much as 70% by releasing Trichogramma platneri on four occasions through the egg-laying period of each of the three successive generations of the codling moth through the season. We have estimated that the best release rate is 200,000 parasitoids per acre for each release, which requires one square from the commercially-available Trichogramma egg cards to be stapled to the lower canopy of each tree in the orchard. In order to make the application of T. platneri in walnut orchards more efficient and acceptable to growers, it is important to be able to develop a broadcast application technique that will deliver the Trichogramma parasitized eggs into the canopy of the orchard from a tractor-mounted applicator. In this project we are testing a commercially-available Bio-Sprayer designed for delivering beneficial insects on to tree foliage. The Bio-Sprayer system applies a slurry of parasitized eggs in a Bio-Carrier that effectively sticks them to the orchard foliage. We are currently evaluating the survival and performance of the Trichogramma through four steps in the application process; submersion in the slurry tank, coating the parasitized eggs in the sticker, propulsion from the applicator to the tree foliage, and field exposure in the tree canopy. During the 1966 season we will also determine the pattern of distribution of parasitized eggs within the tree canopy to calibrate the application rate of the Trichogramma.
Final Reports for Biological Control Projects that Ended in 1995 MANURE REMOVAL AND BIOCONTROL OF FLIES Impact of staggered manure removal schedules on pest flies and associated natural enemies in caged-layer poultry housing.
Principal Investigators: B.A. Mullens, Entomology, Riverside; N.C. Hinkle, Entomology, Riverside
Summary of Accomplishments: We studied whether removing alternating rows of accumulated manure helps preserve natural fly predators and thus improves fly control. Three open-style caged layer poultry ranches on manure buildup systems were studied for 10 cleanout cycles in all seasons for 2 years. Seasonal timing of cleanout is perhaps the most important consideration. Disturbing accumulated manure in March, April or May has a high probability of causing problems with little house flies (Fannia spp.) for 4 to 8 weeks following cleanout. Late summer or early fall cleanouts (August and September) may result in problems of similar duration with house flies (Musca domestica). Based on our observations, the best times to clean out in southern California probably are June (before house fly season but after Fannia season) and December (before the worst of Fannia season and after house flies have subsided). However, any disturbance of accumulated manure carries some risk of fly resurgence. Past UC research has shown that flies are less abundant when a pad of dry manure is left. This was assumed to reflect carryover of beneficials and better drying of the new manure. The pad harbors fewer residual predators immediately after cleanout; over half of the fly larvae and predaceous beetles, and over two-thirds of the predaceous mites are removed. Cleanout disturbance causes movement of mobile predators (beetles), which may enhance recolonization. Experiments indicated that absorption of moisture from the fresh droppings by a pad is minimal. Drying action by the pad is due to height (better air flow). In summer, manure on the floor is almost twice as wet after a week when compared with manure elevated by 5 to 6 inches. This is very important for fly control. Fly predators rebounded fairly quickly, especially the mites, which recolonized disturbed manure better when undisturbed manure was adjacent. Predatory beetles did not recolonize more efficiently in alternate cleanout houses. We did not monitor fly parasites and cannot extrapolate the predator results to them. Alternate row removal usually had no significant advantage over simultaneous removal for fly control. Over all ranches and seasons, fly numbers were depressed 4 to 15% in alternate row cleanout houses compared with normal cleanout houses; most of this is likely due to slightly better predator performance. However, the advantage is not statistically significant. Alternate row removal of manure probably would not be worth it to most producers who have this type of open housing.
BIOCONTROL OF RUSSIAN WHEAT APHID
Our first breakthrough came during the second year when overwintering recoveries were made at two of our early release locations. These recoveries enabled us to quickly hone in on the most effective of the three parasites: Aphelinus albipodus and Aphelinus asychis. Further releases and large scale recoveries during the next two field seasons made it clear that A. albipodus, a species collected from China, was the most effective parasite in our experimental tests. Unlike native parasites, A. albipodus is able to seek out RWA in low numbers during the early part of the season, giving the parasite a strategic advantage in controlling populations of RWA before they can inflict serious damage and before chemical controls are necessary. Most importantly, we observed that A. albipodus can effectively reach aphids that are enclosed in tightly curled grain shafts, an impossibility for the larger native parasites and predators. A. albipodus has additional traits that help it to reduce pest populations even further. In small grains it is a very specific parasite, efficiently concentrating its efforts on RWA; it is also a host feeding species. There are three additional accomplishments of this project. We have been able to effectively use field cages to ensure success in establishing an introduced parasite; we have been able to initiate a reservoir of A. albipodus in a wildlife area where they may be established on a permanent basis and from which these effective parasites can move into adjacent small grains to combat RWA infestations; and we found that when plants receive adequate water insecticides did not increase yield.
BIOCONTROL OF THE EUCALYPTUS LONGHORNED BORER Introduction and establishment of natural enemies of the eucalyptus longhorned borer (Phoracantha semipunctata) in California.
Principal Investigators: J.G. Millar, Entomology, Riverside; T.D. Paine Entomology, Riverside; L.M. Hanks, Entomology, Riverside
Summary of Accomplishments: The eucalyptus longhorned borer (ELB) is a devastating pest of eucalyptus that has killed tens to hundreds of thousands of eucalyptus trees since its introduction into California around the early 1980s. Its range now includes most of Southern and Central California, and it is continuing to spread northwards. We have introduced, mass reared, and released five species of parasitic wasps to control this pest. One species, the egg parasite Avetianella longoi, is firmly established throughout Southern California, and at at least one site in Central California. Parasitism rates in naturally laid egg masses are >90%. We have evidence that a second parasitoid species, Syngaster lepidus, successfully overwintered and is establishing at two release sites.
SEARCHING FOR AN EFFECTIVE WHITEFLY PARASITE
Durations of some behavioral activities, such as assessment of the host for oviposition and host feeding of the whitefly by the parasites, were strikingly different among the plant species. We repeated these studies for parasites raised on different host plants with selected quantifiable differences to evaluate the role of the natal host plant on parasite searching ability, host plant species selection, and other short-term behavioral adaptations. We discovered that the searching and host selection behaviors and percentage oviposition of wasps raised on different host plant species were not different on the parental host plant or on any of the other plant species tested. Three greenhouse studies were conducted on parasitoid searching behavior. The first of these examined E. sp. nr. californicus searching behavior on smooth and hairy-leaved melon plants. Significantly higher proportions of whiteflies were parasitized on the smooth-leaved melons. In studies examining the effects of resin producing and nonresin producing hairs, the data show that percentage parasitism was not different among smooth and hairy melon types in the presence of other host plant species. The type and nature of hairs present on a plant may be more important in influencing parasitism than the presence of hairs per se. Further, parasitoid searching was more intense on plants with higher whitefly densities irrespective of leaf hairiness. These studies suggest that parasitism of whiteflies is not enhanced on melon plants with smooth surfaces, which might make searching by parasitoids easier when other, more preferred host plants are available. In the field, less-preferred plant species may provide sites relatively free from parasitism.
MICROBIALS FOR TURF PESTS Biological control of the scarab, Cyclocephala hirta, in turf with the bacterium, Bacillus popilliae.
Principal Investigator: H.K. Kaya, Nematology, Davis
Summary of Accomplishments: We conducted three trials which indicated that there were problems with the spores of the milky disease bacterium, Bacillus popilliae (BP), or with the insect. The problems that we encountered were (1) the inability of the Cyclocephala hirta (designated as Oakmont) BP spores to infect C. hirta, and (2) the low infectivity of the Japanese beetle BP spores to infect C. hirta. The C. hirta BP spores which were produced in 1991 and stored at room temperature were not as infectious as they once were. The reason for this is not clear, but we hypothesize that the C. hirta BP spore and the parasporal body are enclosed very loosely within a sporangium making them less stable during storage. We believe that fresh spores should be highly infectious. However, we cannot rule out the possibility that the physiological state of the grub makes them less susceptible to the C. hirta BP spores. We doubt that the grubs are more resistant to the BP spores. The low infectivity of Japanese beetle BP spores to C. hirta grubs suggests that this might be the normal situation as has been observed by others. The higher rate that we observed previously may have been because the grubs were stressed and therefore more susceptible to infection to the Japanese beetle BP spores. Attempts to infect C. pasadenae grubs with the high concentration of BP spores were not successful. There was a natural BP infection in these grubs. We believe that BP is a viable control agent for white grubs in California. However, we must determine the factor(s) that adversely affected the infectivity of the BP from C. hirta.
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