Annual Reports

1998—UC IPM Competitive Grants Program

Biological Controls

Biological 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.

Investigator must describe how proposed practices could fit into the current production or management systems and detail mechanisms for transferring methods or tools to field use.

New Projects Funded for 1997-98 (none)
Continuing Projects Funded for 1998-99
Projects that Ended in 1997-98
Final Reports for Projects that Ended in 1997

Continuing Projects Funded for 1998-99

Evaluation of Inoculative Releases of Goniozus legneri for Navel Orangeworm Control in Almonds.

Principal Investigator: K. M. Daane, Center for Biological Control, Berkeley/Kearney Agricultural Center, Parlier

Objectives: Determine the effect of Goniozus legneri release practices on the population levels of navel orangeworm and Goniozus legneri, and navel orangeworm nut infestation levels.

Determine the effect of incomplete winter sanitation on population levels of Goniozus legneri and consequent navel orangeworm parasitism and nut infestation levels.

Summary of Progress: There has been increased use of insectary-reared natural enemies for the control of insect pests. We are evaluating the release of Goniozus legneri for control of the navel orangeworm (NOW), Amyelois transitella (Walker), a moth pest of almonds. In 1996, we showed that (i) parasite release in gelatin capsules resulted in significant parasite mortality, (ii) commercial release programs had variable results, from a 0 to ~45% reduction in NOW, and (iii) leaving overwintering nuts on the tree does not consistently increase G. legneri numbers. In 1997, we focused efforts on G. legneri release methods and parasitoid biology, especially during the overwintering period, to determine methods to consistently produce the higher parasitism rates (e.g., >30%). We found that G. legneri released as pupae in gelatin capsules had >80% mortality, resulting from three ants species (Formica aerata, Solenopsis xyloni, and Solenopsis sp.) which killed G. legneri pupae and even some adults. In field release trials, we released adult G. legneri and found good movement throughout the tree canopy. There was also considerable movement between trees, although in sampled transects there was a reduction in percentage parasitism at distances >10 trees from the release site. As in past years, we found the greatest obstacle to the establishment of high densities of G. legneri was overwintering mortality, especially egg and larval stages. Incomplete winter sanitation of "nut mummies" provided refuge for NOW but did not consistently increase G. legneri percentage parasitism, although number were higher at harvest in one study plot. We strongly recommend winter sanitation.

Principal Investigators: R. F. Luck, Entomology, Riverside; J. G. Morse, Entomology, Riverside; K. M. Daane, Center for Biological Control, Berkeley/Kearney Agricultural Center, Parlier

Objectives: Evaluate the potential of several parasitoid species as biological control agents against soft scale pests on citrus (black scale in Southern California and citricola scale in the San Joaquin Valley).

Evaluate black and brown soft scale as rearing hosts for mass-rearing of the most promising parasitoids.

Develop quality control criteria for insectary production of promising parasitoids.

Summary of Progress: We evaluated four parasitoids for augmentative biological control of citricola scale on San Joaquin Valley oranges. Known numbers of Metaphycus helvolus, M. Staleyi, M. luteolus, and M. flavus were released into sleeve cages with citricola scale-infested terminals. We conducted three releases, one on 1 Nov. 1996, 31 Dec. 1996, and 2 Feb. 1997.

The results suggest that M. flavus is the most promising candidate against citricola scales. However, we do not yet know how M. flavus will perform when it is not confined inside sleeve cages.

We are currently performing similar experiments to evaluate parasitoids of black scales. If M. flavus proves effective against black scale, biological control of this pest may become less costly than with the currently used M. helvolu . M. flavus can be reared on brown soft scales which are easier to rear than, black scale. Additionally, one single scale can be used for the production of a parasitoid which is effective against both citricola and black scale.

M. flavus is a newly imported species from an area in Turkey which has a similar climate to that of the San Joaquin Valley (hot summers and relatively cool winters). M. flavus also seems to be able to exploit relatively small scales.

A single synchronized generation of citricola scales per year results in a time period when there are practically no small scales present. The ability to exploit smaller scales will widen the parasitoids’ opportunities for reproduction and survival and thus, may crucially contribute to the success of biological control.

Principal Investigator: S. E. Lindow, Plant and Microbial Biology, Berkeley

Objectives: Determine the extent to which the population size of an antagonistic bacterium which is a registered biological control agent is enhanced on pear and apple in the presence of surfactants with very low surface tension.

Determine if the biological control of fire blight disease and frost injury to pear and apple is greater in the presence of a surfactant with very low surface tension than when the antagonist is applied in water alone.

Summary of Progress: Since the biological control of fire blight disease caused by the bacterium Erwinia amylovora by biological control agents such as Pseudomonas fluorescens strain A506 is maximized when the biological control agent has completely colonized the target plant tissue before the arrival of the pathogen, we investigated whether silicon-based surfactants having low surface tension could facilitate colonization and hence biological control. Populations of strain A506 were as much as 5-fold higher on pear flowers treated with a mixture of strain A506 and Break-Thru (0.05%) than on flowers treated only with strain A506 in two field trials. On some, but not all dates, populations of strain A506 were also higher on flowers of Fuji apple when applied on conjunction with Break-Thru. Break-Thru did not increase the severity of fruit russet to apple or pear when applied by itself compared to control trees and russet severity was lower on trees treated with a mixture of strain A506 and Break-Thru; russet severity was similar on trees treated with strain A506 alone and in combination with Break-Thru. The incidence of fire blight disease was too low in plot areas in 1997 to evaluate the effect of surfactants on biological control of fire blight disease, although the higher population sizes of strain A506 on trees treated with a mixture of Break-Thru and strain A506 would suggest that enhanced disease control would have been achieved.

Projects that Ended in 1997-98

Electronic Spot Spray Applicator for Ant Management in Orchards and Vineyards.

Principal Investigators: K. Giles, Biological and Agricultural Engineering, Davis; P. A. Phillips, UC IPM Project, UC Cooperative Extension, 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.

Summary of Progress: The preliminary system for electronic detection and spot spraying for orchard and vineyard trunks has been designed and assembled. The system consists of an ultrasonic range detector, an electrically-actuated spray valve and nozzle, a pressurized spray reservoir, a data interface system and a laptop computer for control and data collection. A small microcontroller has been programmed to operate the system. The system uses ultrasonic detection of a spray target. Once the target is detected, a spray emission from the valve/nozzle is started and continues for a preprogrammed duration of time. A specialized spray nozzle and control valve have been designed and fabricated to allow an accurate stream to be quickly directed to a target area. The spray system provides 2-3 m of projection of a spray stream, independent of liquid pressure or spray pulse rate. When completed, the system will allow trunks, posts and stakes in orchard and vineyards to be automatically sprayed as a vehicle travels along row middles.

Principal Investigators: M. P. Parrella, Entomology, Davis; R. B. Sher, Entomology, Davis

Objectives: Evaluate the performance of Diglyphus begini and Steinernema carpocapsae used together for biocontrol of leafminers, Liriomyza trifolii, under different timing release schedules on greenhouse chrysanthemums.

Verify effectiveness of the best timing release program under commercial greenhouse conditions utilizing commercially grown cucumbers.

Summary of Progress: Over the past six months, we have begun greenhouse cage experiments on the combined use of Steinernema carpocapsae, an entomopathogenic nematode, and Diglyphus begini, a parasitoid, for control of Liriomyza trifolii, a leafminer, on chrysanthemums. We have started trials testing the relative efficacy of the two agents on leafminer-infested chrysanthemums when the agents are used alone or in combination. In the combination trials, we are testing which timing of parasitoid/nematode release schedule works best (most effective leafminer control and most parasitoid survival). The timing schedules are 1) nematodes sprayed on the plants first followed by wasp release either immediately, two days later, four days later or six days later and 2) wasp released on the plants first followed by nematode sprays either immediately, two days later, four days later or six days later.

In addition to the greenhouse cage experiments, we are preparing for large-scale greenhouse trials in a cucumber crop at Seminis Seeds in Woodland, CA. In order to provide the large numbers of parasitoids necessary for these trials, we are increasing our leafminer/parasitoid colony and building a new colony where we will have mass-production of parasitoids reared exclusively on cucumbers. The second colony is necessary both for numbers of parasitoids needed and to ensure that the parasitoids are reared on the same host plant on which they will be released.

Final Reports for Projects that Ended in 1997

Precision, Carrierless Handling and Placement of Biocontrol Organisms.

Principal Investigator: K. Giles, Biological and Agricultural Engineering, Davis

Objectives: Determine if biocontrol organisms can be electrically charged to useful charge/mass ratios; and, to determine the biological effects of electric fields on the viability of biocontrol organisms in the egg stage.

Summary of Accomplishments: Theoretical and experimental analyses investigated the possibility of using electric charging and fields for conveying biological control organisms. Mathematical analysis, conducted prior to the experimental period, showed that triboelectric charging was unlikely to produce useful charge-to-mass ratios for the relatively large, high-moisture content eggs. However, a series of field exposure tests indicated that eggs could likely withstand the high electric fields typical of corona and contact charging. Moreover, analysis of the highest possible charge-to-mass ratio (based on dielectric breakdown of air) on eggs and the likely mass flow rate of a field-worthy egg dispensing system, indicated that space charge alone would likely be inadequate for manipulating egg trajectories. Therefore, supplemental electric fields would be required. These analyses implied that corona charging would be used rather than triboelectric charging. In such a case, metering of the eggs into the charging device would present a significant design challenge. Additionally, accurate metering and dispensing of undiluted (carrierless) eggs could alone greatly improve the application process.

The metering of undiluted lacewing eggs was investigated using a three-phase traveling field conveyor design. The flow rate of eggs discharged from the tunnel was measured by collecting the emitted eggs. A detailed experiment investigated the relationship between flow rate and frequencies for sinusoidal electrical waves. Results indicated that voltage and frequency can be used to control the flow rates of individual insect eggs. This technique could be used for field metering and application of eggs.

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