1a. Objectives (from AD-416):
Determine if and which fungicides cause lethal of sublethal effects on blue orchard bees in field, caged, and laboratory studies. Also assess almond nut yield according to placement of blue orchard bee nesting sites within commercial orchards.
1b. Approach (from AD-416):
Work will be performed during early spring in large (>100 acre) trials and commercial almond orchards in California over five years. Visual observations of blue orchard bee adults at nesting sites before and after fungicide sprays will determine if and how the fungicides change bee foraging or nesting behavior. In nest observations of immature bees will determine if fungicides inhibit development or kill larvae. Chemical analyses of mass provisions will determine if bee food is contaminated with fungicides. Cage studies will all for testing specific fungicides and their surfactants or other mixed products in order to define how and what components are deemed detrimental to bee reproduction, longevity, or survival. Further screening for effects of fungicides on behaviors related to learning and memory will be performed in the laboratory. Additionally, nest occupancy by bees according to nesting site placement will be matched with yield of nuts at various distances from nesting sites throughout the orchards. Analyses will reveal effects of the distribution of nesting bees on nut yield.
3. Progress Report:
The objective is to determine if and which commonly-used orchard fungicides cause lethal or sublethal effects on blue orchard bees. In 2011, we used cage studies near Bakersfield, California for testing two fungicides and a surfactant in order to define how and what components are deemed detrimental to bee reproduction, longevity, or survival. Inside the cages (n = 6), observations were made of adult bee activity at the nest sites, and daily cell production was recorded. Data analysis indicates a behavioral change in actively nesting bees at the nest sites that inhibits efficient nesting. In 2012, application of fungicides were made in a designated area of an almond orchard where blue orchard bees had been released, but very few bees nested in this area and, thus, did not allow for examining the effect of the fungicides. Similar fungicide research in cages also was done on alfalfa leafcutting bees in 2012 to compare with blue orchard bee results. Electroantennagram studies were performed on blue orchard bees exposed (through ingestion) and unexposed to three different fungicides in the laboratory. No difference was found in the responses of the two groups of bees to floral cues, and, therefore, there is no indication that fungicides disrupt the ability of antenna to detect olfactory stimuli. However, ingestion of fungicides did increase adult bee mortality. The statistical analyses and reporting of this study continues. The intended impact of this project is to determine if there is a need to safeguard bees from fungicide applications during almond bloom.