Location: Invasive Species and Pollinator Health
Project Number: 2030-22000-033-001-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Oct 1, 2021
End Date: Jun 30, 2023
The objectives of this project are to: 1) survey regions in South and East Africa for additional natural enemies of bagrada bug; 2) survey regions in California infested with bagrada bug for resident natural enemies that use this insect as a host or prey, as required for a field release permit of candidate parasitoid; 3) continue host specificity testing of novel biocontrol agents as required for a field release permit of candidate parasitoid.
The USDA ARS European Biological Control Laboratory (EBCL) in France has established a cooperative agreement with the University of Stellenbosch in the western cape area, South Africa to collect parasitoids attacking bagrada bug eggs. A similar agreement has been developed with Kenya Agricultural and Livestock Research Organization (KALRO) in Kenya. In both of these countries, staff trained by EBCL personnel will use sentinel bagrada bug eggs obtained from laboratory cultures to capture egg parasitoids. The recent discovery in California of a Gryon species, the primary candidate species under testing, Gryon aetherium, has added a new component to our field surveys of natural enemies. This parasitoid emerged from wild bagrada bug eggs found through sifting soil from underneath plants heavily infested by this pest. In order to determine the parasitism rate and distribution of this species in California, we will survey for it across the current range of bagrada bug in California using a new sampling technique. The new technique will use sifted soil placed on trays under plants heavily infested by bagrada bug in order to provide an attractive egg laying medium for bagrada bug females. Sand trays will be placed at 6 to 10 locations in Monterey (Salinas Valley) and Sonoma counties, including the two locations where G. aetherium was collected in 2018 and 2019, at least three times during the season, in mid-summer (late July to early August), late summer (late August to September) and fall (October to November). Trays will also be placed at least monthly from July to October at one site in Solano County where G. aetherium was collected in 2020. Sand trays will be placed in or near crop fields and patches of known weed hosts of bagrada bug. Host specificity testing will be measured in two phases, first using ‘no-choice’ testing followed by ‘choice’ tests. During the first phase the parasitoid will be exposed to just one species of egg. Those non-target stink bug species successfully attacked by the candidate parasitoid will be subjected to ‘choice tests,’ whereby the parasitoid is exposed simultaneously to eggs of two stink bug species: bagrada bug and one of the non-target stink bugs. Eggs will then be monitored and numbers of emerging parasitoids (by sex) and days to parasitoid emergence will be recorded.