Annual Reports

1998—UC IPM Competitive Grants Program

Biorational Use of Biotic Agents or Chemicals

This biorational use 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 plant growth regulators, 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 is also considered if on-going research has shown that no reasonable alternatives exist.

New Projects Funded for 1998-99
Continuing Projects Funded for 1998-99
Projects that Ended in 1997-98
Final Reports for Projects that Ended in 1997

New Projects Funded for 1998-99

Evaluation of Mass Releases of Two Parasites of Vine Mealybugs, Planococcus ficus (Signoret) in the Coachella Valley.

Principal Investigator: D. Gonzàlez, Entomology, Riverside

Objectives: Assess impact from ants on parasite effectiveness.

Assess impact form mass releases of two parasites, against vine mealybugs,

Determine their optimal effectiveness in either establishment or augmentation programs.

Combine most effective vine mealybug control methods for grower assessment in demonstration plots.

Principal Investigator: N. J. Mills, Environmental Science, Policy and Management, Berkeley

Objectives: Determine physiological host range and host preference of Trichogramma platneri under laboratory conditions.

Evaluate ecological host range of T. platneri under field conditions.

Determine the influence of temperature and food availability on longevity of T. platneri within the tree canopy of walnut orchards.

Investigate the effect of release rate and tree height on dispersal of T. platneri from commercial walnut orchards.

Continuing Projects Funded for 1998-99

Introduction and Evaluation of Parasitoids Attacking Aphids as a Component of the Developing IPM Program on Prunes in California.

Principal Investigators: N. J. Mills, Environmental Science, Policy and Management, Berkeley; L. K. Etzel, Environmental Science, Policy and Management, Berkeley

Objectives: Acquire, import and produce nonindigenous species and biotypes of parasitoids that attack prune aphids. Field release the parasitoids and then collect them from release sites for distribution to new localities.

Monitor parasitoid establishment and impact on pest aphids in prune orchards, and establishment on aphids on the obligatory alternate host plants in California.

Survey for and monitor the populations of native arthropod parasitoids and predators that attack prune aphids in California orchards and on their alternate host plants.

Summary of Progress: The mealy plum aphid, Hyalopterus pruni, is an exotic pest which has become an important problem in prunes in California with the reduction of in-season insecticide sprays for peach twig borer (Anarsia lineatella). From mid-April to early October in 1997, 10,000 specimens of three Spanish biotypes of the exotic parasitoid Aphidius colemani were produced and released against the mealy plum aphid at 10 prune orchard sites and 5 cattail (an alternate host) sites in Glenn, Butte, Sutter and Yolo counties. Branches where parasitoids were released in sleeves were examined for the presence of mummified aphids two weeks after the releases. Although the numbers of mummified aphids found were quite erratic, differences among the parasitoid biotypes were noted, with the Barcelona and Enguera biotypes producing more parasitized aphids per sleeve than the Valencia biotype. Recoveries were made in all orchards where parasitoids were released and from several of the cattail sites.

Detailed sampling of orchards to determine the abundance of aphids, indigenous predators, and released parasitoids was performed from mid-March until November in four orchards in Glenn, Butte, and Sutter counties. The two orchards with younger trees, that continued to show vigorous growth throughout the season, supported 30-40 times the aphid populations present in the two older orchards. Low levels of parasitism by A. colemani was detected through the sampling program in all four orchards. The dominant indigenous predators were the lacewing Chrysopa nigricornis, the ladybird beetles, Harmonia axyridis and Hippodamia convergens, and the aphid fly Leucopis sp.

Disease Forecast Model for Controlling Blackmold in Tomato.

Principal Investigators: M. D. Cahn, UC Cooperative Extension, Sutter/Yuba counties; R. Michael Davis, Plant Pathology, Davis

Objectives: Develop a computer based disease forecast system to optimize fungicide timing for controlling blackmold (Alternaria alternata) in tomato.

Determine the period for A. alternata infection under different regimes of relative humidity, leaf wetness, and air temperature.

Evaluate timing of fungicide application on control of blackmold disease.

Develop and validate a forecast model for blackmold disease.

Contribute to a regional disease forecasting system.

Summary of Progress: Tomato fields located in the south Sacramento Valley were monitored for blackmold disease during July, August, and September of the 1997 growing season. Weather conditions including relative humidity, dew, and air temperature, were also monitored to identify the conditions that promote disease. Data collected during the 1997 growing season was statistically analyzed and developed into a preliminary disease forecast model. The model will be tested in subsequent seasons and modified to improve disease prediction.

Fungicide field trials were conducted at two locations to examine the effect of application timing and number of applications on blackmold disease control. Results from both sites showed that timing of fungicide applications had no effect on disease control. Disease control improved with increasing number of fungicide applications. Trial results contradicted conclusions from trials of past years that have shown that timing of fungicide applications can significantly affect disease control. However, weather conditions may have been conducive for blackmold disease for the duration of the field trials.

A masters student in the UCD Plant Pathology Department has begun laboratory and greenhouse experiments to determine environmental conditions that promote blackmold disease infection in ripe tomato fruits. The results of these experiments will aid the development of an accurate disease forecast model that growers will be able to used to time spray fungicides to maximize control of blackmold disease.

Synergism of Imidacloprid and Entomopathogenic Nematodes: a Novel Approach to White Grub Control in Turfgrass.

Principal Investigators: H. K. Kaya, Nematology, Davis; A. M. Koppenhöfer, Nematology, Davis

Objectives: Test the feasibility of combinations of the chloronicotinyl insecticide, imidacloprid (IMI), and entomopathogenic nematodes (EN) for the control of white grubs in turfgrass. Determine the effect of combined applications of IMI and EN on third instar masked chafer, Cyclocephala hirta, and Japanese beetle, Popillia japonica, the direct effect of IMI on EN infective juveniles, and the effect of IMI on EN recycling in white grub hosts.

Determine the pathogenicity of S. kushidai and its capacity to recycle in various life stages of Cyclocephala.

Summary of Progress: We observed a synergistic effect of combinations of the synthetic insecticide imidacloprid and entomopathogenic nematodes on mortality of third instar grubs of the masked chafers Cyclocephala hirta and C. pasadenae. In greenhouse pot experiments, this synergism occurred whether imidacloprid and nematodes were applied simultaneously or nematode application was delayed by 14 d. Nematode species had a significant effect on the interaction. Thus, the most consistent synergism occurred between Steinernema glaseri and imidacloprid but the interaction between Heterohabditis bacteriophora and imidacloprid, although weaker, was also synergistic. Steinernema kushidai, on the other hand, did not interact with imidacloprid or was even antagonistically affected by the insecticide.

Laboratory studies with S. kushidai showed that third instar grubs were the most susceptible Cyclocephala life stage and produced the highest number of nematode progeny. S. kushidai also caused mortality in the other stages, but considerably less progeny emerged from adults and second instars while no progeny emerged from first instars. These observations suggest that field populations of S. kushidai primarily recycle in the third instars but limited recycling in second instars and adults may contribute to nematode persistence.

Projects that Ended in 1997-98

IMPROVING MONITORING TOOLS FOR WALNUT HUSK FLY

Ecology of Predatory Green Lacewings: Quantifying the Impact of Higher-Order Consumers.

Principal Investigator: J. Rosenheim, Entomology, Davis

Objectives: Measure the seasonal patterns of abundance of green lacewings in tomato fields and grape vineyards and quantify mortality factors acting on lacewings in the egg, larval, pupal, and adult stages.

Quantify the seasonal abundances of other dominant species of generalist predators in tomato fields and grape vineyards and experimentally evaluate their impact on larval lacewing survivorship.

Determine the diet of predatory green lacewings, including their rate of consumption of key tomato and grape pests, through detailed field observations of foraging lacewings.

Summary of Progress: The utilization of generalist predators in biological control systems is increasing, due to the wider adoption of augmentative release strategies using commercially reared natural enemies and due to the increased use of cover crops designed to increase resident populations of generalists. The ecology of these generalist predators, however, is poorly understood. We studied predatory green lacewings and other key groups of generalist predators during the 1996 and 1997 field seasons in six crops in Yolo and Solano counties: grapes, tomatoes, alfalfa, cotton, almonds, and walnuts. We first addressed the question of whether lacewing populations occur naturally in agroecosystems at densities as high or higher than those recommended in augmentative releases. Lacewing populations were found to peak early in the season in grapes for 1996 only (reaching 11,000 per acre), alfalfa (reaching 58,800 per acre in 1996 and 72,000 per acre in 1997), almonds (reaching 23,000 per acre in 1996 and 36,000 per acre in 1997), and walnuts both years (reaching 7,000 and 19,000 per acre in 1996 and 1997, respectively). In cotton the highest numbers (26,000 per acre in 1996 and 51,000 per acre in 1997) were reached during the late summer. No lacewings were recorded in tomatoes in 1996 and densities were very low during 1997 (maximum density of 2000 per acre). Lacewings occurred in crops despite the presence of very low densities of prey species (aphids, mites, and thrips). Variation in lacewing densities between crops, between sites within a crop, and seasonally underscore the importance of sampling fields before recommending augmentative releases; however, in many cases augmentative releases can produce meaningful increases in lacewing densities. Lacewing survivorship through the egg stage, which can be attacked by parasitoids or predators, was generally high (approximately 60-80%). In contrast, only 30% of lacewings survived through the pupal stage, which was also attacked by parasitoids and predators. Oth er dominant predators included spiders, Orius tristicolor, predatory mites, and ants. Direct observations of foraging lacewing larvae show that lacewings feed on extrafloral nectar as well as a variety of soft-bodied arthropod prey.

Final Reports for Projects that Ended in 1997

Establishment and Evaluation of a Biological Control Program Against the Eucalyptus Snout Beetle, Gonipterus scutellatus Gyll.

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 efficacy of A. nitens in controlling populations of ESB, and its impact on damage to Eucalyptus caused by ESB.

Summary of Accomplishments: The eucalyptus snout beetle (ESB) was first discovered in summer 1994 defoliating eucalyptus trees in a citrus orchard windrow in central Ventura County. Since that time, ESB has spread throughout Ventura County, and northward and southward into neighboring Santa Barbara and Los Angeles counties. Populations of the beetle reached epidemic proportions in many areas by 1995, resulting in nearly complete defoliation of eucalyptus. Release of the biological control agent Anaphes nitens, a minute parasite of the beetle’s eggs, has rapidly brought ESB under control.

Anaphes nitens has proven adept in dispersing and locating infestations of ESB on eucalyptus trees, and has naturally colonized all areas were ESB infestations have been discovered to date. Parasitism rates of A. nitens commonly exceed 90% of ESB eggs, and this high mortality rate has resulted in a sharp declines in the abundance of ESB larvae within a few month’s time. By killing a high proportion of beetle eggs, the parasitoid has allowed recovery of eucalyptus trees at sites that were earlier defoliated, and has prevented defoliation in sites where the beetle has recently colonized. In most areas, A. nitens is such an effective biological control agent for this severe pest that no further control measures need be taken.

Principal Investigators: T. J. Michailides, Plant Pathology, Davis/Kearney Agricultural Center, Parlier; B. A. Holtz, UC Cooperative Extension, Madera County; C. Hong

Objectives: Determine the importance of Monilinia fructicola apothecia as a source of primary inoculum in stonefruit orchards in the San Joaquin Valley.

Study the conditions that favor the stromatization of mummified fruit by M. fructicola that enhance 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.

Summary of Accomplishments: Apothecia of the brown rot pathogen, Monilinia fructicola, of stone fruit were commonly observed in February and March in commercial orchards during a disease survey and in experimental orchards where stonefruit mummies were added. Several millions of ascospores can be released by each apothecium at the beginning of the season. Conidial sporulation of M. fructicola was not observed either on mummified fruit, peduncles, or blighted flowers and twigs. Mummies, however, produced conidia under laboratory conditions. Blossom blight was less severe in research plots where mummies were removed than when mummies were left on the ground. Subsequently, preharvest fruit brown rot was also less severe in plots where mummies were completely removed than where infected fruit were left on the ground. A similar relationship was observed for postharvest fruit brown rot in both 1995 and 1996. In addition, preharvest fruit brown rot was reduced in plots where the orchard floors were disced, herbicides were applied to berms in the tree rows, and mummies were removed in comparison with plots where no till, no herbicide, and no removal of mummies were practiced. These results suggest that apothecia can function as a main source of primary inoculum for initiating brown rot epidemics in stonefruit orchards of the San Joaquin Valley; and that blossom blight and fruit rot can be reduced by removing mummies from orchard floors or by preventing the development of apothecia after discing and/or applying herbicides during winter.

Apothecia were produced in February and early March from stromatized mummies that were placed in the orchard soil only in October, November, or December. Stromatized mummies placed in the field in August/September and January/February did not produce apothecia, presumably because they did not have the proper conditions for apothecia development. Apothecia were never produced from nonstromatized or fresh fruit mummies, and laboratory results confirmed these field studies. Therefore, growers who knock infected fruit to the ground before October (preferentially immediately after harvest) can break the life cycle of the brown rot fungus by preventing fresh mummies to become stromatized and by subjecting the mummies under conditions favorable to destruction.

Field fruit brown rot was less severe in plots where thinned fruit were removed than where thinned fruit were not removed and where the thinned fruit were added in five orchards in both 1995 and 1996. Postharvest brown rot was also less severe in treatment plots, from one nectarine orchard in 1996, where thinned fruit were completely removed than where thinned fruit were not removed. No difference was observed in both pre and postharvest brown rot of fruit from treatment plots where thinned fruit were racked from "dry" berms into "wet" irrigation drenches than when thinned fruit was left untouched in two nectarine orchards. Our results suggest that thinned fruit can function as a significant source of secondary inoculum for M. fructicola and brown rot disease can be reduced by destroying thinned fruit.

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

Objectives: Field test two different trap types (yellow panel and green ball) and three lures (Trece Supercharger, Pacoast membrane-release lure and the walnut volatile caryophyllene) in three commercial walnut orchards, each in a geographically distinct area of northern California, to give information to develop a walnut husk fly trap that will better detect or predict onset of egglaying so that pesticide sprays can be better timed.

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

Summary of Accomplishments: Over a two year period, we field tested two trap types (yellow sticky panel and green sticky ball) and different lures/attractants for monitoring walnut husk fly (WHF). In the first year, yellow sticky panel traps baited with ammonia (either Trece Supercharger or Pacoast membrane lure) were found to be more effective but less selective WHF traps than green sticky ball traps baited with caryophyllene (a walnut odor). In the second year, yellow sticky panels baited with ammonia again captured the greatest numbers of flies, although 100% caryophyllene was more effective in attracting flies than 10% caryophyllene regardless of trap type. In both years, traps hung high in the tree canopy captured more flies than traps hung low in the canopy.

Caryophyllene lures showed peaks in attractancy which approximately corresponded to the onset of WHF egglaying in walnuts. Nevertheless, these peaks in trap capture coincided so closely with onset of damage that growers would not be able to rely on this type of trap to predict onset of WHF oviposition. We determined that the most effective way to predict onset of WHF egglaying was to dissect female WHF captured on the traps for presence of eggs in their ovaries. Both years mature eggs were detected in female flies approximately 10 days before stings or eggs were found in walnuts, allowing growers one week to treat before damage occurred.

We developed new guidelines for WHF monitoring traps, including recommended trap type (yellow panel trap baited with Trece Supercharger), trap placement (in the top 1/3 of tree canopy in known husk fly hot spots or in dense shade), optimal trap evaluation (dissection of female WHF to detect mature eggs), and timing of treatment (within one week of detection of mature eggs in females). These recommendations have been disseminated in the form of a video (Walnut Husk Fly: Biology, Monitoring and Control) and have been tested statewide.

We decided to omit the Pacoast membrane-release ammonia lure and instead test a lower concentration of the walnut volatile caryophyllene in year two. Previous studies indicated that 10% caryophyllene might be just as effective as 100%. The Pacoast ammonia lures and the Trece Supercharger ammonia lures captured similar numbers of flies in year one, making a second year of testing with both of these lures unnecessary.

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