Project Number: 2080-21000-019-29-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2020
End Date: Aug 31, 2023
The objectives of the proposed work is as follows: 1) Determine the degree to which pesticides undergo transfer from alfalfa leaves to provisions inside alfalfa leafcutting bee (ALCB) nests and from soil partitions to provisions in blue orchard bee nests. The experiments described will be conducted with two pesticides commonly used for pest control in alfalfa fields (e.g., chlorpyrifos and lambda-cyhalothrin) and orchards (e.g., pyraclostrobin, bifenthrin, and lambda-cyhalothrin); and 2) Develop a predictive model for pesticide movement from leaves and soil into pollen provisions to determine risk of exposure to solitary bees and bumble bees via pollen provisions.
Part 1, Year 1: Percent Lipid Determination in ALCB Provisions. We hypothesize that pesticide transfer rate will be affected by the relative lipid quantities in alfalfa leaves and ALCB provisions due to the strong affiliation that non-ionized pesticides have with lipids. Since percent lipids in alfalfa leaves is known, the percent lipid in ALCB provisions will be determined using pressurized liquid extraction and percent lipid will be determined gravimetrically. UV-Vis spectra of all extracts will be measured to indicate relative quantities of lipids in extracts. These analyses will be performed on provisions from different sources/regions to assess variability. Part 2, Year 1: Development and Validation of Analytical Methods for Pesticide Quantification in Provisions. To measure pesticide transfer rates, pesticides in alfalfa leaves and ALCB provisions will be quantified using in lab-constructed (faux) nest cells. With methods developed for quantifying pesticides in alfalfa leaves and honey bee pollen samples, we will quantify pesticides in ALCB provisions. A selective pressurized liquid extraction to extract pesticides from ALCB provisions will be developed by (a) identifying appropriate sorbents and sorbent amounts to use in extraction cells for adequate retention of matrix components during extraction and (b) verifying target pesticides are adequately extracted from provisions. Matrix retention will be assessed using a combination of gravimetric and UV-Vis analysis, as described for lipid determination. Target analyte recovery will be assessed with spike and recovery experiments. Extractions will be performed to determine optimal conditions to achieve low matrix interference and high percent recoveries of target analytes. Pesticide quantification will be conducted via GC-MS/MS. Part 3, Years 1 & 2: Pesticide Transfer Experiments. The rate at which pesticides transfer from alfalfa leaves to ALCB provisions in faux nest cells will be determined. For ALCB, we hypothesize that transfer of pesticides from leaves to provisions in nests may be an important exposure route for ALCB larvae. Alfalfa leaves will be contaminated with pesticides by immersion in a hexane/pesticide solution and dried. Faux cells will be made using pesticide-contaminated leaves and clean pollen provisions inside short glass tubes with the same diameter as ALCB nesting holes and then incubated at 25°C in a closed container. For each pesticide, provisions and leaves will be sampled over time to determine the extent and rate of transfer into provisions. Years 2 & 3. Similar experiments will be done with blue orchard bees: 1) examining natural soil partitions and provisions from nests and 2) making faux cells to demonstrate pesticide transfer from soil to provisions. Further testing will be done for both bee species to examine the effect of adjuvants on pesticide transfer rates, effects of various temperatures on transfer rates, and transfer rates of other classes of pesticides. Finally, we will develop a predictive model for pesticide movement from leaves and soil into pollen provisions to determine risk of exposure to solitary bees and bumble bees via pollen provisions.