Project Number: 2080-21000-019-076-I
Project Type: Interagency Reimbursable Agreement
Start Date: Sep 15, 2023
End Date: Sep 14, 2026
Objective 1: Develop an integrated pest management approach to control lygus bug and alfalfa weevil without the use of chlorpyrifos. Objective 2: Test the use of selective versus broad-spectrum insecticides on natural enemies. Objective 3: Determine the safety for alfalfa leafcutting bees of insecticides used in Lygus bug control. Objective 4: Create a comprehensive flow chart to provide insight on insecticide applications to control problematic insect pests of alfalfa while protecting pollinators and other beneficial arthropods.
ARS researchers will be responsible for aspects of the work proposed in Objectives 1-4, and will lead Objective 3. In Objective 3, cage trials in Years 1-2 will be used to determine if exposure to insecticides used for Lygus control result in sublethal effects on alfalfa leafcutting bees (Megachile rotundata), such as reduced foraging effort or reproductive output. Twelve screened field cages will be erected over a planting of alfalfa located at the ARS Pollinating Insects Research Unit (PIRU) in Logan, Utah. A bee shelter with a polystyrene bee board with 49 cavities will be erected in each cage. In each cage we will release 40 males and 20 individually paint-marked female leafcutting bees. Activity of individually-marked females at the nesting block will then be recorded for 1 hour a day M-F for three weeks. During the first week, no applications will be made and normal activity will be recorded. At the start of the second week, applications will be made to the alfalfa at night, including control cages where only the other ingredients (no active ingredients) are used, as well as one cage where nothing is sprayed. Amount of time during a pollen foraging trip will be recorded, as well as number of attempts to enter the incorrect nest. This will allow us to see if normal behavior is impacted by exposure to pesticides. Reductions in foraging activity could reduce the number of bees visiting flowers and have detrimental outcomes for yield. Additionally, all completed nests will be x-rayed to determine the number of cells per nest. Half the completed nests will then be frozen to end development and dissected to remove pollen provisions, which we will analyze for pesticide residues at the Cornell Chemical Ecology Core Facility, which uses a modified QuEChERS method. The other half of the completed nests will be allowed to develop normally, and the number of emerging adults will be recorded in the following spring. These data will allow us to determine how different pesticide applications to the crop relate to residue levels in provisions, and if residues in the pollen provisions effect bee development.