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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Research Project #433199

Research Project: Suitability of the Gall Forming Mite Aceria genistae for Redistribution as a Biological Control Agent of Scotch Broom

Location: Invasive Species and Pollinator Health

Project Number: 2030-22000-027-04-I
Project Type: Interagency Reimbursable Agreement

Start Date: Apr 1, 2017
End Date: Mar 31, 2019

1. Determine the host specificity of the Scotch broom mite Aceria genistae. a. Quantify non-target use under field conditions in the few areas that the mite has colonized in California forests. b. Conduct host range tests to quantify environmental safety of this mite. 2. Submit an APHIS permit request to redistribute the mite to Scotch broom infested forests. Compile data and prepare a redistribution proposal for consideration by regulatory agency Technical Advisory Group (TAG, APHIS).

The methods used herein will investigate the use (i.e., galling or feeding damage) by A. genistae of species that are close relatives of Scotch broom and thus at greatest risk, including other broom species (exotics) and native Lupinus species. Two experiments will be conducted: Survey of non-target use in-situ: The distribution of A. genistae in California is being monitored by USDA and California Department of Food and Agriculture (CDFA) scientists. Current populations are limited to select Scotch broom patches in Mendocino, Del Norte, Siskiyou, Shasta, Nevada, Amador, El Dorado and Placer Counties. Areas of high mite densities will be surveyed for brooms and native Lupinus species and in-situ assessments of host use will be quantified. Mites collected on the non-target plants will be preserved in 95% EtOH and submitted to USDA’s Systematic Entomological Laboratory for identification. Host range testing: Host range testing will be conducted outdoors under natural environmental conditions at the Exotic and Invasive Weeds Research Unit facility in Albany, California. Test plants will be placed on one of six bench tops in a randomized complete block design, with the position of each plant species within a group assigned randomly. Inclusion of test plants will be influenced on species discovered in proximity to field surveys described above. However, three broom and four perennial lupine species have already been acquired for the study based on known sympatric distributions: Scotch broom (Cytisus scoparius), French broom (Genista monspessulana), Spanish broom (Spartium junceum), big leaf lupine (Lupinus polyphyllus), silver bush lupine (Lupinus albifrons), Parish's stream lupine (Lupinus latifolius var. parishii), and yellow coastal bush lupine (Lupinus arboreus). Five additional annual lupines have been identified and will be acquired or propagated when funding is secured. Scotch broom galls containing A. genistae mites will be collected from field sites in the Sierra foothills (near the towns of Volcano, Amador County, and Garden Valley, El Dorado County) by clipping stem sections containing galls, and transporting to the lab in zip lock bags within coolers. Inoculations will continue approximately once per month, as long as fresh galls are available in the field. Approximately three weeks after inoculation and at monthly intervals thereafter, test plants will be visually assessed for any signs of discoloration or deformity that could be attributed to A. genistae feeding. Counts of mites per sample and galls per plant will be compared with ANOVA, using the randomized complete block design.