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Funded Project

Funding Program: Regional IPM Competitive Grants - Northeastern

Project Title: Habitat and Resource Management to Enhance Biological Control in Greenhouses

Project Directors (PDs): Jan Nyrop [1] John Sanderson [2]

Lead State: NY Lead Organization: Cornell University

Research Funding: $58,844

Start Date: Aug-15-2010 End Date: Aug-14-2011

Pests Involved: western flower thrips

Site/Commodity: greenhouses, nursery

Area of Emphasis: biocontrol, biological control

Summary: Biological control holds the promise of sustainable and safe control of the most important greenhouse arthropod pest, western flower thrips. Release of the mite predator Amblysieus swirskii can lead to biological control, but often does not. Even though growers and extension educators have shown broad interest in biological control, a lack of consistent and reliable effectiveness impedes widespread adoption. We hypothesize that a solution is available and propose through a one-year effort to demonstrate this and set the stage for commercial-scale trials. Research has revealed that the predator, A. swirskii, quickly leaves plants that lack both leaf hairs (leaf trichomes) and a supplemental food source (pollen) and many greenhouse-grown plants are trichome free. We propose to mitigate this limitation by applying artificial leaf hairs (low densities of tiny fibers) and pollen to the canopy of plants lacking these resources. Over a twelve month period we will complete three objectives: (1) We will determine the influence of several types of artificial leaf trichomes and of several species of pollen on retention of and oviposition by Amblyseius swirskii and determine the influence of these pollens on oviposition by western flower thrips (WFT). (2) Based on these results we will determine the influence of select artificial leaf trichomes and pollen on the short-term dynamics of interacting populations of A. swirskii and WFT. (3) This will set the stage for conducting small greenhouse trials to determine the influence of artificial trichome and pollen augmentation on the effectiveness of biocontrol of WFT using A. swirskii. Objectives: 1) Determine the influence of several types of artificial leaf trichomes and of several species of pollen on retention of and oviposition by Amblyseius swirskii (AS) and determine the influence of these pollens on oviposition by western flower thrips (WFT). 2) Based on the results from Objective (1), determine the influence of artificial leaf trichomes and pollen on the short-term dynamics of interacting populations of AS and WFT. 3) Based on the results from Objective (2), conduct small greenhouse trials to determine the influence of artificial trichome and pollen augmentation on the effectiveness of biological control of WFT using AS. Proposal USDA CRIS data

Final Report:

Outcomes Specific outcomes for objectives are as follows beginning with objective 1 in which we identified a fiber material and pollens which could be used to enhance the suitability of plant habitat for mites. These tiny fibers must be in close contact with the leaf surface to mimic the mite habitat provided by leaf trichomes. The leaf texture of plants including impatiens, pepper, basil, and pansy was sufficiently smooth that application of an adhesive (dilute white glue) was necessary for the applied fibers to remain attached. On beans fibers with glue approximately doubled the retention of A. swirskii compared to fibers without glue. None of our originally proposed fiber materials (cellulose, jute, paper pulp) were sufficiently effective at increasing mite retention. The material that most consistently produced results was an acrylic yarn that had been pulled apart into strands and hand cut into very small lengths. Achieving an even distribution of any of the fiber materials required breaking up clumps of the raw fibers. The system ultimately used in objectives 2 and 3 consisted of shaking over the plant canopy a plastic cup with wire mesh covering the opening and several wingnuts dropped into the fiber material. Of the pollens tested, apple, cherry, and plum pollens are commercially available in quantities suitable for orchard applications and are promising for use along with the fiber technology. As the pollens are somewhat stickier than cattail pollen, we continued using cattail for our remaining objectives. Objectives 2 and 3 were conducted simultaneously using plants from the same lot. Results from the two experiments differed in A. swirskii effectiveness but not in the impact of fibers. On the individual impatiens in objective 2, the A. swirskii decreased the abundance of thrips relative to the no phytoseiid control. There was however, no consistent, clear impact of fibers and/or pollen on the abundance of A. swirskii or thrips. The densities of A. swirskii after 19 d were 2.5 to 3.5 times greater than the original 10 mites released. In objective 3 with large patches of impatiens, the A. swirskii failed to reduce thrips abundance compared to the untreated control. Although fibers alone and with pollen were associated with decreased thrips abundance, there was no impact of fibers or pollen on A. swirskii. Our objectives were designed to identify a fiber material that enhanced mite abundance on single plants and then proceed to scale up the application technology. Mid-way through the project it became apparent that the lack of scaled-up application technology itself was inhibiting our ability to assess the impact of fibers and pollen on predatory mite abundance. Two issues in particular were problematic. First, although bean plants lack leaf hairs there is sufficient leaf texture for trichome mimics to stick just a little, thus allowing applied fibers to stand upright and resemble natural leaf hairs. Impatiens leaves are entirely smooth and our best performing fibers simply fell off. Spraying dilute white glue on leaves as a non-toxic adhesive prior to fiber application improved this issue and provided sufficient data to request funding from the Pest Management Alternatives Program (PMAP). This additional funding has enabled us to collaborate with colleagues with engineering expertise and work is underway to develop a system that will work well for plants with very smooth leaf textures and is suitable for small scale commercial trials. Second, while conducting the PMAP work we have determined that it is critical for at least a small amount of fiber material to penetrate the leaf canopy and adhere to the underside of the leaves. These two issues appear to be the driving force in the lackluster response of the mites to fibers in the experiments presented above and the key limitations in moving the technology closer to commercial testing.

Impacts Safeguarding human health and the environment: Insecticides are inherently biologically active compounds and have attendant human health and environmental risks. Because biological control reduces insecticide use, there is concomitant reduction in human health and non-target risks. Predatory mite releases have previously been shown to reduce the number of pesticide applications needed to control western flower thrips. When available for use commercially, technology to enhance mite habitat through application of fibers is expected to increase predatory mite effectiveness and further reduce insecticide use to control thrips. Economic benefits: Because weekly releases of predators will not be necessary with a successful trichome and pollen augmentation technology, cost of the predators themselves and labor to apply them will decrease. It may also be possible to decrease predator release rates, further reducing the cost of thrips biocontrol. Implementation of IPM: The immediate impact of this research project is generation of the knowledge required to pursue commercial-scale trials including: 1) knowledge of predatory mite response to various types of fiber materials and commercially available pollens that could be used to enhance plant habitat for the mites and 2) an understanding of the parameters necessary for predatory mites to respond well to artificial trichome applications (small amount of non-toxic adhesive for fibers to stick up like natural trichomes, at least small amounts of the fibers must adhere to the lower leaf surface during application). In combination with additional funding from the Pest Management Alternatives Program (PMAP) to develop an application device based on the results of this Northeast IPM project, it is expected that small scale commercial trials will be possible within the next year. The ultimate impact of the proposed work will be to make biological control of thrips a reality in many, and perhaps most, greenhouses in the northeast, particularly given the current interest in thrips biocontrol among growers. Updates on this project were presented to research and extension personnel in the Greenhouse symposium at the 2011 Entomological Society of America meeting in Reno, NV and a summary of results to date published in the IOBC/WPRS working group bulletin.

Report Appendices Final Report 2012 [PDF]

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