2009 Annual Report
1a.Objectives (from AD-416)
We propose to investigate alternative chemistries for control of lygus bugs in alfalfa seed, and predacious beetles in alkali bee beds. Pollination by leafcutting bees, Megachile rotundata, or alkali bees, Nomia melanderi, is essential for seed set in alfalfa seed production. Bee mortality that results from inadvertent exposure to pesticides, disease, parasitism, or direct predation can negatively impact seed yield. In-field pesticide use recommendations are based on the safest timing and bloom conditions for given chemicals, but data on pesticide toxicity to many new chemicals are unknown. In addition, alkali bee nests are subject to predation by ground-dwelling predacious beetles. Azinphos-methyl is the only registered pesticide for control of these predatory beetles, but it only has been granted a 24C registration through 2012, this use will not extend any further due to the fact that the product will no longer be manufactured. Additionally, azinphos-methyl is an extremely toxic insecticide. Thus, alternative controls are needed.
1b.Approach (from AD-416)
We seek to identify compounds that are effective at controlling pests, but that are safe to pollinating bees in alfalfa seed crops. To identify such compounds, we will use three different tests: (1) large-scale, replicated alfalfa seed field tests using 20-acre blocks treated with candidate compounds for lygus control; (2) laboratory bioassays where leafcutting and alkali bees are exposed to treated alfalfa plants; and (3) monitoring of alkali bee beds in Washington state to determine beetle populations. After initial populations are assessed, we will treat the plots with several insecticidal treatments. ARS will provide expertise in bee biology and how to handle the bees for development and mortality studies. The University will conduct the experiments, analyze the data, and write up the reports.
Large-scale field trials were conducted in grower fields to evaluate insecticide efficacy and pollinator safety. Fields that had been commercially treated (during bloom) with Rimon, Rimon, and Dibrom, and Beleaf were monitored for pests and bees. There appeared to be no direct bee mortality in these commercial fields as a result of exposure to these commercial applications. Laboratory bioassays were also conducted to evaluate insecticide safety to pollinators. Alfalfa leafcutting bees were exposed to residues of the pesticides. The pesticides were applied to 0.01 acre plots of alfalfa, and the residues allowed to age for one hour in the field. The adults were observed, and mortality evaluated. Percent mortality was corrected based on the control mortality after 24 hours of exposure. The clothianidin (Belay) and acetamidprid (Assail) caused the greatest mortalities (95 and 53%, respectively). Other mortalities were below 15%. Experiments were initiated in looking for alternatives to azinphos methyl for predacious beetle control in alkali bee nesting beds. Study sites were establised on representative bee beds in the Touchet-Gardena area of Walla Walla County. The ADODR monitored the progress on this project through various methods including telephone conference calls, site visits, and meetings to discuss project plans and accomplishments, validate project expenditures, and provide technical advice.