EVALUATION OF POTENTIAL BIOLOGICAL CONTROL AGENT FOR EGERIA DENSA (BRAZILIAN WATERWEED) IN THE SACRAMENTO-SAN JOAQUIN DELTA
Exotic and Invasive Weeds Research
2011 Annual Report
1a.Objectives (from AD-416)
Evaluate efficacy, applicability and utility of Hydrellia spp as a biological control agent for management of Egeria densa.
1b.Approach (from AD-416)
Efficacy and host specificity will be determined using standard, accepted methods for assessing feeding (with and without alternative host plants) and reproductive behavior both in the country of origin (Argentina) and under certified quarantine glasshouse and growth chamber conditions at Albany, CA. Range of water depths of feeding impacts will be determined using field sampling and multi-depth culture systems in Argentina. Developmental timing and temperature required for growth, reproduction and dispersal will be assessed to compare with conditions in proposed release site (Sacramento-San Joaquin Delta).
This agreement was established in support of Objective 1 of the inhouse project, the goal is to develop potential biological control agents for Brazilian Water Weed. Efficacy of the fly Hydrellia sp. was further characterized at the USDA South American Biological Control Laboratory (SABCL) in Argentina. This appears to be a new species and shows promise in reducing upper water-column biomass of Brazilian waterweed. In anticipation of importing this natural enemy into California. Temperature controlled culture systems were installed at the Albany quarantine facility. These culture systems will be used to raise and test the efficacy of Hydrellia sp. to examine Brazilian waterweed phenology in anticipation of approvals to release Hydrellia into the open environment. Similar culture systems were obtained for the ARS-Davis facility so that the growth and development of Brazilian waterweed and typical native plants could be examined further. Field sampling for aquatic insects was conducted monthly at potential release sites in the Sacramento-San Joaquin Delta. Insects are being identified to provide a baseline for assessing the efficacy of Hydrellia spp. when approval for release is obtained. Additional field assessments and surveys in the native (Argentina) range of Hydrellia sp. will be completed during 2010-2011.