Location: Beneficial Insects Introduction Research Unit
Project Number: 8010-22000-031-107-I
Project Type: Interagency Reimbursable Agreement
Start Date: Apr 24, 2025
End Date: Sep 30, 2026
Objective:
The goal of this agreement is to continue evaluations of Diyinius sinicus. The objectives include (1) evaluating the effect of host plants on the foraging efficiency and offspring fitness of D. sinicus; (2) evaluating the effect of host-feeding and food provision on egg maturation and reproductive potential of D. sinicus; and (3) improving simple rearing and cold-storage methods of D. sinicus. These studies will be done in close collaboration with APHIS project partners.
Approach:
Objective 1: Host plant effects on foraging efficiency and fitness of D. sinicus
ARS will investigate the effects of host plants tree-of-heaven (TOH vs grapes) on the host-feeding preference, parasitism rate (foraging efficiency), and parasitoid development ratein no choice tests. SLF nymphs will be reared on potted grapes and TOH trees, respectively. The nymphs will be reared on the corresponding plants at least for 10 days before they are used for the tests and they will reared only on their assigned host plant. Individual female wasps (about one week old, mated) will be first exposed to 30 first instars and 30 second instars of SLF nymphs for one week on a potted plant of one plant species in cage, and then exposed to 30 first instars and 30 second instars of SLF nymphs for another week on a potted plant of another plant species, or vice versa. There will be 20 replicates for each exposure order. All exposed hosts will be checked to record the numbers of both first and second instar hosts parasitized, host-fed, and percentage of superparasitism. All parasitized hosts will be reared to record the survival of parasitized offspring (i.e., developed into cocoons), developmental time to cocoon as well as offspring sex ratio. A sub-sample of cocoons will be measured for the body-size to determine the relative offspring fitness.
Objective 2. Factors affecting egg maturation of D. sinicus ARS will investigate the parasitoid’s egg maturation dynamics. Newly emerged male and female wasps after cold storage will be paired (to ensure successful mating, each female will be paired with 2 males at least for the first week). Each female will be provided with (1) honey only in vails for two weeks; and (2) honey + nymphs (30 first instars and 30 second instars every week) on potted TOH in small cage for two weeks. Female wasps will be dissected after 7- or 14-day to determine the number of mature eggs (also measured for the body size). Ten females will be dissected per age treatment. In addition, 10 newly emerged females will be dissected (as control) to determine if the female emerges with some mature eggs. All dissected females will be checked for the ovary developmental status (photos taken). All exposed first and second instars of SLF nymphs will be checked for oviposition or host feeding and all parasitized hosts will also be reared on potted trees to collect cocoons.
Objective 3. Improving simple rearing and cold-storage methods for D. sinicus
For mass-rearing, simple methods of rearing D. sinicus and stockpiling cocoons need to be developed. ARS will rear this parasitoid on SLF nymphs on potted TOH plants under the laboratory conditions (22°C, 16L:8D and 40-60% RH) inside incubators. Cocoons produced before September from above experiments or rearing will first be held at 5 °C (complete dark) in vails inside a 100% RH humidity box for one month and then held under the laboratory conditions (22°C 16L:8D and 40-60% RH) to determine the emergence. Cocoons produced since September will be stored at 5 °C (complete dark) in vails inside a 100% RH humidity box (dark) for 3 or 6 months to determine the survival of cold-stored cocoons.
