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The Colorado potato beetle (CPB; Leptinotarsa decemlineata) is a serious pest of potatoes nationwide. Efforts to develop host resistance to CPB have yet to produce commercially acceptable varieties; however, CPB host preference, survival, reproduction, and defoliation vary among wild potato, its cultivated relatives, and some commercial potato varieties. <P>In a pilot study, we recorded as high as nine-fold differences in defoliation rates among ten organically produced potato varieties. We will conduct a more detailed investigation into variation among commercial potato varieties in regard to CPB host preference and susceptibility to defoliation and yield loss from CPB feeding damage. Variety-specific defoliation and yield data will allow economic analysis of potential returns and risks of organic versus commercial potato production in this region. <P>This project will contribute to the development of sustainable organic potato production in several ways: (1) growers could produce less preferred varieties to limit CPB damage with fewer insecticide applications or (2) tailor a CPB management strategy to a variety's susceptibility; (3) reduced insecticide use would satisfy consumer demand for environmentally responsible production, (4) mitigate against insecticide resistance development, and (5) reduce input costs; moreover, (6) varieties that are particularly attractive to CPB ultimately could be used in a trap cropping program. <P>The use of more tolerant or less preferred varieties could be part of an overall integrated pest management strategy to reduce insecticide use and environmental risks while increasing yields and contributing to the long-term sustainability of organic potato production. <P>The outreach plan is comprised of a coordinated effort among the University of Idaho (UI) Extension system, the Idaho Potato Commission, and the Northwest Coalition for Alternatives to Pesticides (NCAP; Eugene, OR). Specific extension activities will include several annual organic field days during the growing season that will focus on management of Colorado potato beetles and allow attendees to observe our research plots; workshops and presentations at the highly attended Idaho Potato Conference; publication of results and recommendations through the UI Extension system, NCAP network, national trade journal magazines (e.g., Spudman and Potato Grower), and eXtension and eOrganic Community of Practice; and dissemination of findings to the scientific community via journal publications and scientific meeting presentations.
Non-Technical Summary: The Colorado potato beetle (CPB) is one of the most important pests of potato production in the United States. Given the limited insecticide options for organic producers, high expense of organic insecticides, and well-founded concerns over development of insecticide resistance in CPB, sustainable management tools for organic potato producers are sorely needed. The primary objective of this project is to clarify differences among commercial potato varieties in regard to CPB preferences and defoliation rates in order to establish the relative susceptibility of commonly grown commercial potato cultivars to CPB damage. Field experiments will be conducted at the University of Idaho Kimberly Research & Extension Center (Kimberly, ID) comparing the abundance of different life stages of CPB (eggs, small larvae, large larvae, and adults) and defoliation rates over time among different commercial potato varieties. A total of at least ten different varieties will be used. The results will allow for evaluation of host preference of CPB and the importance of beetles on defoliation and yield within each variety. Variety-specific defoliation and yield data will allow economic analysis of potential returns and risks of organic versus commercial potato production in this region. This project will contribute to the development of sustainable organic potato production in several ways: (1) growers could produce less preferred varieties to limit CPB damage with fewer insecticide applications or (2) tailor a CPB management strategy to a variety's susceptibility; (3) reduced insecticide use would satisfy consumer demand for environmentally responsible production, (4) mitigate against insecticide resistance development, and (5) reduce input costs; moreover, (6) varieties that are particularly attractive to CPB ultimately could be used in a trap cropping program. The use of more tolerant or less preferred varieties could be part of an overall integrated pest management strategy to reduce insecticide use and environmental risks while increasing yields and contributing to the long-term sustainability of organic potato production. <P> Approach: Objective 1: Compare the abundance of different life stages of CPB and defoliation rates among commercial potato varieties with and without organic insecticide treatments. A field experiment will be conducted at the University of Idaho Kimberly Research & Extension Center (Kimberly, ID) comparing the abundance of different life stages of CPB (eggs, small larvae [first and second instar], large larvae [third and fourth instar], and adults) and defoliation rates over time among different commercial potato varieties and two insecticide treatments (untreated and organic insecticide program). A total of at least ten different varieties will be selected from each of the following groups: Russets, Reds, Blues/Purples, Yellows, and Chipping/Whites. Three-row plots will be arranged in a randomized complete block design and will be replicated at least five times. The numbers of CPB of each life stage per plant as well as percent defoliation will be compared among treatments over time using repeated measures Analysis of Variance (ANOVA). Potato emergence rates, vigor, late-season senescence, and yield parameters (total yield, grade and size profiles, and specific gravity) within the center row of plots will be compared among treatments using ANOVA or repeated measures ANOVA as appropriate. Objective 2: Compare CPB performance and defoliation rates on commercial potato varieties in no-choice assays on caged plants in the field. The same varieties used in Objective 1 will be grown in the field, infested with CPB eggs, and caged to prevent further colonization of beetles. Potatoes will be grown without insecticides in hand-planted, one-plant plots that will be caged in the field before immigration of adults. The plots will be arranged in a randomized complete block design and will be replicated 6-8 times. The number of individuals of each life stage as well as percent defoliation on each plant will be recorded weekly and compared among treatments using repeated measures ANOVA as described for Objective 1. Objective 3: Develop enterprise budgets that will compare costs and returns associated with organic potato production for different varieties and pesticide treatments in the region, and compare them to commercial potato production with various pesticide scenarios. We will organize organic stakeholder meetings with organic potato growers and other stakeholders in order to discuss and develop enterprise budgets for various organic potato varieties and pesticide scenarios. Growers will provide expert opinion regarding which organic insecticides are typically used against CPB, including application rates and the typical number of applications per season. Cost of production data will be used to create enterprise budgets by variety and by pest management practices. Objective 4: Provide research findings from Objectives 1-3 to producers, peers, and other stakeholders in a timely manner through presentations, workshops, field days, newsletters, bulletins, web sites, and other appropriate means.