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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Research Project #445047

Research Project: Discovery and Pre-Release Evaluation of Weed Biocontrol Agents

Location: Invasive Species and Pollinator Health

Project Number: 2030-22000-033-024-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: May 1, 2023
End Date: Jan 31, 2026

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 native range of cheatgrass for new populations of known candidate biocontrol agents, as well as for discovery of new candidate agents.

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) New cheatgrass populations will be sought and inspected for the presence of natural enemies by various means, including sweep netting, field inspection, and collection of cheatgrass for laboratory dissection and emergence of insects in the laboratory.