Progress 09/01/10 to 08/31/13
Target Audience: Target audiences included growers, industry representatives, and other attendees of the Snake River Pest Management Research Tour during June 2011, the Idaho Potato Conference during January 2012, a “Grower’s Own” organic conference during January 2012, and an Organic Field Day at U-Idaho Kimberly during July 2012. A forthcoming publication will target fellow scientists. Changes/Problems: The no-choice caged field experiment was compromised due to the high infestation levels of beetles surrounding the cages; large numbers of newly eclosed adult beetles from the second generation surfaced within cages. Unfortunately, this aspect of the project had to be abandoned. What opportunities for training and professional development has the project provided? Approximately seven undergraduate technicians were involved in assisting with data collection during the life of the project, which provided training for these students in carrying out agricultural field research. How have the results been disseminated to communities of interest? Results were presented togrowers, industry representatives, and other attendees of the Snake River Pest Management Research Tour during June 2011, the Idaho Potato Conference during January 2012, a “Grower’s Own” organic conference during January 2012, and an Organic Field Day at U-Idaho Kimberly during July 2012. A forthcoming publication will target fellow scientists. What do you plan to do during the next reporting period to accomplish the goals?
What was accomplished under these goals?
A two-year field study was conducted at the University of Idaho Kimberly Research & Extension Center (Kimberly, ID) comparing tuber yields and the abundance of different life stages of CPB over time among different commercial potato varieties and two insecticide treatments (untreated and organic insecticide program). Ten different varieties were selected: ‘Russet Burbank,’ ‘Classic Russet,’ ‘Defender Russet,’ ‘Yukon Gold,’ ‘Yukon Gem,’ ‘Dark Red Norland,’ ‘Red Lasoda,’ ‘Purple Viking,’ ‘All Blue,’ and ‘King Harry’ (a variety bred for tolerance to CPB and other insect pests). The insecticide-treated plots were treated with two applications of spinosad (Entrust) against the first generation of CPB and neem-based and/or pyrethrin insecticides as necessary thereafter for the second generation. Comparisons between the untreated and insecticide-treated plots allowed for evaluation of the importance of CPB on defoliation and yield within each variety. Three-row plots were arranged in a randomized complete block design replicated five times. At weekly intervals beginning at the onset of natural infestation of adults onto plots and continuing about ten weeks, all CPB life stages (eggs, small larvae [first and second instar], large larvae [third and fourth instar], and adults) were counted on five plants within the center row of each plot and estimates of the percent defoliation on the same plants were made. The numbers of CPB of each life stage per plant as well as percent defoliation were compared among treatments over time using repeated measures Analysis of Variance (ANOVA). Yield parameters (including total yield, grade and size profiles, and specific gravity) within the center row of plots were compared among treatments using ANOVA. Yields differed significantly between insecticide treatments and among varieties during both years for most grade profiles (total, USDA #1, USDA #2, and culls). Not surprisingly, yields were higher for insecticide-treated plots. King Harry, which was bred for resistance to several insect pests, exhibited higher yields than most other varieties; other high-yielding varieties included Purple Viking, Yukon Gold, and Dark Red Norland. Russet Burbank yielded well the second year, but not the first. All Blue and Classic Russet tended to yield poorly during both years. King Harry produced the most tubers per ha in both years; Purple Viking produced tubers with the highest mean mass in both years. Classic Russet produced the fewest tubers per ha in both years; All Blue exhibited the lowest mean tuber mass in both years. As the field was colonized by adult beetles, initial “preferences” for certain varieties were observed; however, these preferences shifted from week to week and were not entirely consistent between years. Egg abundance tended to reflect adult preferences, but also shifted, which is consistent with females preferring to lay eggs on less infested plants. Differences among varieties in regard to larval abundance and defoliation rates were weak; however, certain varieties tended to show smaller differences in yield between insecticide-treated and untreated plots. For example, during 2012 both Dark Red Norland and Red Lasoda showed similar yields whether treated with insecticide or not, despite exhibiting significantly heavier defoliation when not treated. Other varieties (notably Classic Russet) showed 2-4 fold higher yields when treated with insecticides. Though not part of the proposed project, we rated harvested tubers for wireworm damage. Significant differences were observed among varieties, with at least four varieties exhibiting relatively low damage compared to the other six varieties. Wireworm damage was generally higher on insecticide-treated plots, which was likely a reflection of a greater mass of tubers to attract wireworms. These results, not detailed further here, will be further investigated in future studies.
Progress 09/01/10 to 08/31/11
OUTPUTS: The two field experiments described in the proposal were conducted - an open choice experiment in which Colorado potato beetle responses to ten potato varieties were examined (with and without organic insecticides) and a no choice experiment in which individual caged plants each were infested with the same number of eggs. In addition to collecting data on all life stages of beetles on each plot, data were also collected on plant emergence, tuber yield and quality at harvest, and wireworm damage to harvested tubers. Preliminary analysis of data was conducted. Plots were shown to growers, industry representatives, and other attendees of the Snake River Pest Management Research Tour during June 2011. PARTICIPANTS: Erik Wenninger (PI): directed the entomological portions of the project, including all insect sampling, building and deployment of beetle cages, and spraying of insecticides. Nora Olsen (co-PI): directed planting and harvesting of research plots and fertility and irrigation requirements. Neyle Perdomo (technician): assisted with insect sampling. Mary Jo Frazier (technician): obtained all potato seed, developed plot layout, and organized harvest activities. Kathleen Painter (co-PI): work on the project will commence during the next reporting session. Jennifer Miller (cooperator): work on the project will commence during the next reporting session. Paul Patterson (cooperator): work on the project will commence during the next reporting session. TARGET AUDIENCES: Target audiences included growers, industry representatives, and other attendees of the Snake River Pest Management Research Tour during June 2011. PROJECT MODIFICATIONS: The no choice experiment was compromised due to the high infestation levels of beetles surrounding the cages. Large numbers of mature larvae from the first generation dropped to the soil surrounding the cages to pupate, and newly eclosed adult beetles from the second generation emerged from the soil inside of cages. The no choice experiment will be established using caged plants in a greenhouse during 2012 and/or on a field site that does not have such heavy beetle pressure.
Responses of beetles to the different varieties in the open choice experiment were dynamic from week to week. No one variety was consistently attractive or unattractive to adult beetles, but rather beetles were significantly more abundant on different varieties each week, at least up until the fifth week of sampling when there were no longer any differences in preference observed. Abundance of eggs showed similar shifts that appeared to reflect preferences of adults. Differences among varieties in abundance of larvae and defoliation rates were small, possibly due in part to the very high abundance of beetles overall. During the second year of the experiment, we plan to take more frequent beetle counts and defoliation ratings during critical times (e.g., when adults are first infesting plots and when larvae are starting to defoliate plants), which may help to clarify more subtle differences among varieties. The no choice experiment was compromised due to the high infestation levels of beetles surrounding the cages; large numbers of newly eclosed adult beetles from the second generation emerged within cages. The no choice experiment will be established using caged plants in a greenhouse during 2012. Yield data are still being analyzed, but overall insecticide treatment improved yields across all varieties except King Harry which was bred for resistance to Colorado potato beetles. As expected, yields were generally higher for varieties that were earlier emerging. Wireworm damage differed significantly among varieties, with at least four varieties exhibiting relatively low damage compared to the other six varieties. Wireworm damage was generally higher on insecticide-treated plots, which was likely a reflection of a greater mass of tubers to attract wireworms.
- No publications reported this period