Location: Invasive Species and Pollinator Health
Project Number: 2030-22300-032-15-I
Project Type: Interagency Reimbursable Agreement
Start Date: Aug 13, 2020
End Date: Sep 30, 2020
The primary objective of this project is to continue host specificity testing of two bagrada bug parasitoids, Gryon gonikopalense and Trissolcus hyalinipennis. Establishment of one or more parasitoids specific to bagrada bug will provide persistent, self-sustaining suppression of this pest. No additional inputs or costs would be incurred towards this end once parasitoid populations have spread across the range of the bagrada bug. These parasitoids would provide critical relief to organic producers of cole crops and could reduce the frequency of pesticide applications to conventional production.
Funding supplied by this request will support continued activities by the ARS PI, who will conduct host specificity testing of parasitoids collected in Pakistan. 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. For these tests, clusters of fresh stink bug eggs (<24 h old) will be glued onto card stock strips using drops of Gorilla® glue and placed in glass vials. For no-choice tests, one mated female parasitoid will be released into each vial and removed after 24 hours. The placement of egg strips in choice tests will mimic natural conditions; bagrada bug eggs will be placed on sand on the cage floor and eggs of non-target species will be elevated 6cm from the cage floor on leaves of their preferred host plant. Eggs will then be monitored (for choice tests, egg strips from the target and non-target stink bug species will be placed in separate vials after exposure to parasitoids), and numbers of emerging parasitoids (by sex) and days to parasitoid emergence will be recorded. Eggs without emerging stink bugs or parasitoids will be dissected to record numbers of parasitoid larvae that failed to complete development. This information will help determine the suitability of the different stink bug species as hosts for the parasitoids. Insect cultures will be maintained year-round. Testing will be conducted when eggs of non-target stink bug species are available. We anticipate that most testing will occur during the summer and fall months when both stink bugs and parasitoids are naturally active in the field. Some species of stink bugs will need to be collected from the field since their lab culturing may be extremely difficult. Culturing of native stinkbugs is currently underway. Since 2017 both G. gonikopalense and T. hyalinipennis and have been tested on 11 and 10 non-target stinkbug species; 1-28 replicates of each stinkbug species have been completed for each parasitoid species. In summer to fall 2020 no-choice testing will focus primarily on new non-target species (we anticipate a minimum of three species) and on three species (Banasa sordida, Euschistus servus, Cosmopepla conspicillaris) that did not produce sufficient eggs to complete at least 16 replicates in previous years. Choice tests will also be conducted with four stinkbug species (Holcostethus sp., Banasa sordida, Thyanta pallidovirens, Podisus maculiventris) that G. gonikopalense successfully attacked and emerged from in previous tests.