|Zhu, Kun Yan|
|Throne, James - Jim|
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2012
Publication Date: 7/2/2012
Citation: Chen, H., Zhang, H., Zhu, K., Throne, J.E. 2012. Induction of reproductive diapause in Habrobracon hebetor (Hymenoptera: Braconidae) when reared at different photoperiods at low temperatures. Environmental Entomology. 41(3): 697-705. http://dx.doi.org/10.1603/EN11311. Interpretive Summary: The Indianmeal moth is a major pest of stored grain and processed commodities. There is a small wasp that does not sting humans but naturally parasitizes the Indianmeal moth, and releasing these parasitic wasps would be an environmentally friendly way to control the Indianmeal moth. But, there is currently no way to store these wasps for when they are needed for controlling the Indianmeal moth. We hypothesized that adult wasps that were in reproductive diapause (a resting stage where they don’t produce offspring) could be stored at cool temperatures until they were needed. We conducted studies to determine the environmental conditions that might induce reproductive diapause in these wasps, and found that the wasps appear to enter reproductive diapause when they are reared at a cool temperature and short daylength (68°F and 10 hours of light). Further tests need to be conducted to determine whether these wasps that appear to be in reproductive diapause can be stored at cool temperatures without reducing their performance. Being able to store these parasitic wasps in a refrigerator will enable mass production of the wasps for release for pest management.
Technical Abstract: Development of the parasitoid Habrobracon hebetor Say (Hymenoptera: Braconidae) at low temperatures was determined to identify rearing conditions that might result in adults that were in reproductive diapause. Diapausing adults would be expected to survive cold storage longer than non-diapausing adults for use in biological control programs. Ovarian development was reduced when H. hebetor females were reared at 17.5 and 20°C, and ovarian development was almost completely stopped when females were reared at short photoperiods at these low temperatures. Rearing H. hebetor at 17.5 and 20°C did not result in diapause of immature stages, but did appear to result in possible adult reproductive diapause. Females reared at short photoperiods had prolonged longevity, took much longer to lay their first eggs, and took much longer to lay 50% of their eggs. They also had lower respiration rates than females reared at longer photoperiods. Females that were reared at conditions that appeared to induce reproductive diapause resumed ovarian development and oviposition soon after transfer to a higher temperature, and respiration rate was three times higher after transfer to a higher temperature. Thus, females reared at short photoperiods at 17.5 and 20°C appear to enter reproductive diapause. Further tests will be required to determine whether these adults in reproductive diapause can be stored longer than nondiapusing adults and whether their performance after storage is impacted by cold storage.