Peter C Ellsworth
Lesquerella, Physaria fendleri (A. Gray) S. Watson, is a mustard native to the western United States and is currently being developed as a commercial source of valuable hydroxy fatty acids that can be used in a number of industrial applications, including biolubricants, biofuel additives, motor oils, resins, waxes, nylons, plastics, corrosion inhibitors, cosmetics, and coatings. The plant is cultivated as a winter-spring annual and in the desert southwest it harbors large populations of arthropods, several of which could be significant pests once production expands. Lygus spp. (Hemiptera: Miridae) are common in lesquerella and are known pests of a number of agronomic and horticultural crops where they feed primarily on reproductive tissues. A 4-yr replicated plot study was undertaken to evaluate the probable impact of Lygus spp. on production of this potential new crop. Plant damage and subsequent seed yield and quality were examined relative to variable and representative densities of Lygus spp. (0.3-4.9 insects per sweep net) resulting from variable frequency and timing of insecticide applications. Increasing damage to various fruiting structures (flowers [0.9-13.9%], buds [1.2-7.1%], and seed pods [19.4-42.5%]) was significantly associated with increasing pest abundance, particularly the abundance of nymphs, in all years. This damage, however, did not consistently translate into reductions in seed yield (481-1,336 kg/ha), individual seed weight (0.5-0.7 g per 1,000 seed), or seed oil content (21.8-30.4%), and pest abundance generally explained relatively little of the variation in crop yield and quality. Negative effects on yield were not sensitive to the timing of pest damage (early versus late season) but were more pronounced during years when potential yields were lower due to weed competition and other agronomic factors. Results suggest that if the crop is established and managed in a more optimal fashion, Lygus spp. may not significantly limit yield. Nonetheless, additional work will be needed once more uniform cultivars become available and yield effects can be more precisely measured. Densities of Lygus spp. in unsprayed lesquerella are on par with those in other known agroecosystem level sources of this pest (e.g., forage and seed alfalfa, Medicago sativa L.). Thus, lesquerella production may introduce new challenges to pest management in crops such as cotton.
Judicious use of pesticides is generally accepted as an important pest-control tactic in integrated pest management programs, but not all pesticides are equally appropriate. When this project began, there was not an appropriate tool or set of criteria available to evaluate how well a proposed pesticide use fit within an IPM program. The Western Integrated Pest Management Center and Western Inter-Regional Project #4 (IR-4) collaborated to develop the IPM Compatibility Guidance Document—a set of criteria and instructions for evaluating the potential IPM fit of a proposed pesticide use. The IPM Criteria Guidance Document includes a set of instructions and examples to help IR-4 project requestors develop a ranking and a short narrative description (termed an IPM Fit Statement by the IR-4 Project) of a proposed pesticide use within an IPM program. The IPM Criteria Guidance Document lists 21 specific factors in eight categories—efficacy, economic benefit, nontarget effects, resistance concerns, environmental fate, worker risk, compatibility with monitoring, and utility as a preventative—with descriptors of affirmative, intermediate, and negative compatibility attributes. A survey of project requestors and their IPM Fit Statement submissions indicates that the IPM Criteria Guidance Document is helpful and its use increased the breadth of IPM factors addressed in IR-4 project requests. The IPM Criteria Guidance Document, as a model for formalizing pesticide ‘fit’ assessment, may have broader application in evaluating pest-management tools for their compatibility in IPM programs.
We tested enumerative and binomial sampling plans developed for Bemisia tabaci (Gennadius) in 3,240 ha of commercial cotton as part of the implementation of a community-wide integrated pest management (IPM) program in Laveen and Tolleson, AZ, in 1994. We compared new field observations to sampling distribution models developed previously for all lifestages, and validated and analyzed the performance of 5 sampling plans based on these models by resampling field data from 129 to 284 sites. Mean-variance relationships for the new data differed statistically from mean-variance models previously developed for adults, but not for eggs or nymphs. Resampling analyses indicated that desired precision (SE to mean ratio) was rarely achieved, on average, by fixed-precision sequential sampling plans. These enumerative sampling plans provided better precision than desired at moderate to high densities of eggs and adults and worse precision than desired at most densities of nymphs. An empirical model relating mean density to the proportion of leaves infested with 3 or more adult B. tabaci was accurate at mean densities
CRC Press, Boca Raton