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.
3. Progress Report
Alkali bee health was monitored in commercial alfalfa seed fields. A hydraulic soil core sampling device that connects to a backhoe and is powered by the hydraulics that would typically be used for a packer plate was constructed and used to sample alkali bee beds. In October 2010, 16 bee beds were surveyed. In the summer, nests in the ground were taken using a previously developed quadrant method, and regression analysis was used to determine whether previous samples of adult bees flying in the fields were adequate to predict subterranean larval abundance in the soil core samples. In total, 96 individual paired samples were collected. Emergence holes in summer and the number of alkali bee larvae collected were analyzed by simple regression. The number of larva collected in core samples was correlated with the number of bee emergence holes per unit area counted in the previous July. We also constructed a “bee sweeper” to capture insects at 1, 3, 5, 7, 9 and 11 feet above the ground to determine the height that bees most frequently fly. Collectively, 21 selected road miles were driven in 4 replicated intervals for a total of 84 miles at 40 mph near alkali bee beds in July, and the average numbers of bees captured per mile was determined. These results indicate that 81 percent of the alkali bees and 87 percent of the leafcutting bees flying over roads are at heights below 7 feet. ADODR monitoring is done by phone call, email, and site visits.