|SCHUMM, ZACHARY - UNIVERSITY OF DELAWARE|
|DIECKHOFF, CHRISTINE - UNIVERSITY OF DELAWARE|
Submitted to: BARC Poster Day
Publication Type: Proceedings
Publication Acceptance Date: 4/15/2017
Publication Date: 4/26/2017
Citation: Schumm, Z.R., Dieckhoff, C., Tatman, K.M., Hoelmer, K.A. 2017. Differences in morphometrics and reproductive physiology between two populations of Trissolcus japonicus, a promising biological control agent candidate for brown marmorated stink bug (Halyomorpha halys Stal) in the US. BARC Poster Day.
Interpretive Summary: not required
Technical Abstract: Trissolcus japonicus (Ashmead), a solitary egg parasitoid of Pentatomidae native to Southeast Asia, has been undergoing host-range testing in U.S. quarantine facilities since 2009 as a candidate for the biological control of brown marmorated stink bug (Halyomorpha halys Stål)(BMSB), an invasive agricultural and nuisance pest now reported in 43 U.S. states. Surveys for natural enemies in 2016 revealed that a wild population of T. japonicus found in Newark, Delaware, is genetically dissimilar to the quarantined Asian colonies contained at the Beneficial Insects Introduction Research Unit in Newark, Delaware. With differing origins, we hypothesized that the populations of T. japonicus may exhibit differences in morphometrics and reproductive physiology. Testing these differences could offer insight to future management of the biological control program for BMSB. The focus of this study was to examine the differences between the Delaware population and a population from Beijing, China, and determine whether these differences are significant enough to warrant further experimentation. To document differences in morphometrics, we reared parasitoids from each population on BMSB eggs (diameter = 1171.6 ± 19.6 µm), and measured the hind tibia length of 25 emerged female parasitoids. To measure fecundity, we set up 30 replicates of a single T. japonicus (age <24 hr) female on a BMSB egg mass (<24 hr), and moved each to a new egg mass every 48 hours until the parent wasp died. After allowing progeny emergence for 4 weeks, we counted emerged parasitoids and then dissected the remaining eggs for undeveloped parasitoids to determine the total number of eggs the parasitoid laid over its lifetime. We compared these two colonies using t-tests to determine if there was significant difference. Our study revealed that the length of the hind tibia was not significantly different between the two colonies (Beijing = 441.4 µm; Delaware =453.2 µm) (p>0.05). However, the Beijing population produced significantly fewer parasitoids per female than did the Delaware population (Beijing average = 124.93 parasitoids; Delaware average = 170.14 parasitoids) (p<0.05). It can therefore be concluded that the two colonies should undergo further testing to explore other differences in morphometrics and physiology, while continuing to add data to these results. Significant differences in fecundity could indicate that the Delaware population may be a more efficacious biological control agent, which may warrant prioritization for distribution, and further comparisons to quarantined populations.