UC Riverside

In an effort to find a biological control agent of Bagrada hilaris, an invasive pentatomid pest on brassica crops in western North America, three hymenopteran egg parasitoids were recovered from brassica plant debris in Pakistan and sent to California, USA for evaluation. One of these, a uniparental species, has since been described as Ooencyrtus mirus. To evaluate O. mirus as a potential biological control agent, I investigated its host range and reproductive capacity. I also tested parameters for maximizing its reproduction, including temperature and the age of the parasitoid and host eggs. Finally, I examined O. mirus’ ability to find host eggs on broccoli plants in soil, where B. hilaris lays them. The results show O. mirus to be a generalist parasitoid species with a preference for B. hilaris. Under lab conditions O. mirus lays an average of 118 eggs and lives an average of 58 days. The immatures undergo quiescence at 14° or 16°C. They can be stored at these temperatures for at least 3 months with no loss of reproductive success. The immatures develop fastest at 36°C, but the best temperature for rearing is 30°C. Above 30°C, the second generation has an increase in the proportion of males, due to the high temperature killing the symbiotic Wolbachia bacteria that enable unfertilized eggs to develop as females. Wasps of age 3-11 days have better reproductive success than wasps aged 0-2 days. They are most successful on 0- and 1-day-old B. hilaris eggs, and they can reproduce on frozen eggs. The ability of O. mirus to find host eggs in soil was poor, and even worse on plants. These studies describe the biological characteristics of O. mirus that suggest it could be an effective biological control agent. However, more testing is needed on its host preferences under natural conditions to determine if it would be safe to release in the field; i.e., not a threat to native or beneficial host species.