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Optimizing Insect Management in Desert Vegetables using a New Reduced Risk Insecticide Technology


The goals and objectives of this project are to first evaluate and compare foliar and soil applied insecticide approaches using novel technologies for cost-effective insect management under a conventional head lettuce production system. In addition, this project will evaluate and compare the economic and residual effectiveness of chlorantraniliprole soil treatments applied to romaine lettuce for insect management under diverse production and irrigation systems. <P> Finally, results of this experimental work will be validated through participatory research that enhances the adoption of this new technology via peer-to-peer collaborations with growers and PCA's via on-farm research trials We anticipate widespread adoption of this new reduced -risk technology over the next several years and implementation of use patterns will be based largely on the recommendations generated from these studies.

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Non-Technical Summary: The American consumer has grown to expect safe, affordable, and high-quality vegetables throughout the year, and lettuce has become an important part in their daily diets. A complex of lepidopterous larvae has become economically challenging to manage in lettuce, and IPM programs to control them rely heavily on a few conventional and reduced-risk insecticides. Because of the increasing risks of resistance, impending regulatory actions, and occupational risks associated with insecticide use, the Arizona and California lettuce industry is seeking cost-effective management alternatives for these pests. The goal of this proposal is to develop and implement new reduced-risk insecticide technology that provides growers with sustainable management approaches for Lepidopteran and other important pests in lettuce. Based on our preliminary findings, we are confident that the alternative approaches discussed in this proposal will lead to significant economic improvements in insect control. Our objectives focus on the rigorous evaluation of several insect management approaches using novel, reduced risk insecticide technologies. We have designed several field studies that should yield not only sustainable, but practical insecticide uses. We place additional emphasis on developing soil insecticide uses for Rynaxypyr in diverse lettuce production and irrigation systems. Nested within all these efforts are studies specifically intended to support the development of a practical resistance management program for this new technology in lettuce. Finally, we propose to enhance adoption of this new insect technology by working collaboratively with growers during the research and implementation process. <P> Approach: Using field plot designs and sampling techniques developed over the past 17 years, we will apply formulated compounds to lettuce plants using foliar and soil application methods. Data will be collected from plots established at the Yuma Agricultural Center. Studies in all three objectives will also be undertaken to measure Rynaxypyr residual activity using field efficacy data, bioassays of larvae on field collected leaves, and concurrent analysis of the chemicals concentration in plant tissue. Five treatments to be compared (foliar and soil applied ) will be replicated four times and arranged in a randomized complete block design. Densities of the three lepidopteran species will be estimated by taking whole plant, destructive samples beginning at stand establishment (2 leaf stage). Evaluation of control will be based on the number of live larvae per plant sampled from the center 2 rows of each replicate twice weekly. The sample unit will consist of visual examination of whole plants for presence of beet armyworm, cabbage looper, and corn earworm larvae. Initially, twenty-five lettuce seedlings plants per plot will be sampled. The effectiveness of management programs on yield and quality will be measured by harvesting the central 20 ft from the middle 2 beds of each plot. Data will also be collected in each year (n=4) from the Rynaxypyr soil treatments and untreated plots to measure insecticide uptake and persistence in lettuce leaf tissue. We will also concurrently estimate larval mortality in bioassays using leaves removed from treated plants at 20, 30 and 40 days following treatments. Our bioassay method will be similar to Palumbo (2002) using a lab colony of second generation beet armyworm and cabbage looper (2nd instar) larvae established from local field collections. Older lettuce leaves will be cut longitudinally along the midrib, and intact halves will be used for larval bioassays and Rynaxypyr determinations. We will specifically correlate the mortality data to both Rynaxypyr field rates, and Rynaxypyr leaf concentrations through time. Analytical quantification of Rynaxypyr will be achieved using a protocol originally derived from DuPont Crop Protection. The procedure is essentially an adaptation of extraction and analysis methods for the neonicotinoid insecticide quantification. The method is based on a rapid and relatively simple extraction procedure where tissue samples will be chromatographically separated with HPLC. Mean seasonal insect densities, yield and quality responses and larval mortality and will be tested for heterogeneity of variances prior to statistical analysis and means transformed if necessary (Gomez and Gomez 1984). We will conduct a one-way analysis of variance for all insect and lettuce data sets with means compared where appropriate using the Ryan-Einot-Gabriel-Welsch multiple F test (P=0.05). Linear regression will be used to describe the relationship between plant uptake of Rynaxypyr concentrations and larval mortality. Finally, validation and implementation of the most cost-effective approaches will be initiated with cooperating growers ad crop consultants in Year 2.

Palumbo, John
University of Arizona
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