Location: Invasive Species and Pollinator Health
Project Number: 2030-22000-033-018-I
Project Type: Interagency Reimbursable Agreement
Start Date: Apr 1, 2023
End Date: Apr 1, 2026
Objective:
The primary objectives of the research covered in this agreement are to 1) Determine whether Aculodes marcelli infestation significantly reduces germination of cheatgrass seeds; 2) Collect pre-pupae of Stenodiplosis tectori for establishment of laboratory colonies; 3) Collect adults of Pachytychius nr. hordei; 4) Conduct field host-association studies of S. tectori and P. nr. hordei; 5) Survey invaded range of cheatgrass for new populations of known candidate biocontrol agents.
Approach:
1) Colonies of A. marcelli will be reared on cheatgrass plants in a greenhouse. Control plants will be sown from seed, grown in a different greenhouse, and inspected regularly to ensure the absence of mites or other natural enemies. Following plant senescence and seed dehiscence, all seeds produced by each plant will be harvested and the number of seeds produced by each plant will be recorded. Seeds will be allowed to dry and will then be tested for germination. Germination rate data will be analyzed to detect differences between infested and control plants. 2) Cheatgrass plants with mature, red-to-brown spikes will be sampled and dissected under a stereomicroscope to search for midge pre-pupae in the florets. This will take place at all cheatgrass field sites from which S. tectori have been collected, in Bulgaria and Greece, from early May to late June. 3) Marked cheatgrass populations will be surveyed using sweep nets from April to early June. Recovered weevils will sent to ARS-SEL for morphological identification with a single leg removed from each specimen for molecular analysis. 4) Field host-association studies will be conducted near a large cheatgrass population in Kalambaka, Greece, from which S. tectori and P. nr. hordei have been collected. All sympatric grass species growing within ~500 m of the cheatgrass population will be sampled at the seed ripening stage for the presence of weevils or midges from the spikes. Cultivated wheat and barley plants will also be sampled from nearby agricultural fields using the same protocol. Any midges or weevils that are collected will be preserved for morphological and/or genetic analysis. Sampling will occur weekly from April to June, to account for differing phenologies among the various grass species. 5) Cheatgrass plants samples will be collected from invasive populations and subjected to eDNA analysis to detect the presence of known or unknown species of natural enemies.
