No-choice assay of Helicoverpa zea on soybean tissues

Helicoverpa zea (Lepidoptera: Noctuidae) is an important insect pest which can cause severe economic damage on soybean. Previous research found that H. zea prefers to oviposit on soybean leaves compared to other tissue types. We hypothesized that female ovipositional choice to different tissues is due to plant volatiles. We designed a no-choice experiment using a one-way olfactometer. We reared larvae under controlled environmental conditions until pupation. We then separated pupae by sex and allowed the moths to eclose. We kept couples together until the females mated and began oviposition. We only used mated females in the test. We tested moth response to the following tissues: flowers, leaves, stems and pods, as well as a positive (whole soybean plant) and negative (water) control. We found that more moths responded to our positive control and leaves compared to the other tissues we tested. This research could benefit breeding programs if volatiles can be adjusted through breeding. Moreover, while H. zea moth, and related species, response to plant volatiles is well-studied, ours is the first study to experimentally demonstrate a response to different soybean tissue types. This finding is important to understanding the overall ecology of this important pest.