Doctor of Entomology (PENTM)
Sweetpotato is affected by a wide variety of viruses worldwide, which can cause yield losses of up to 90%. Many of these viruses are transmitted by aphids in a non-persistent manner. Non-persistent viruses are acquired and transmitted within minutes, and thus conventional control, such as insecticides, are ineffective. Altering aphid movement and feeding behavior may affect the rate of virus transmission. One potential method to alter aphid behavior is volatile organic compounds (VOC), including volatiles emitted by virus infected plants, plant hormones, and commercial control agents. Aphid movement near sweetpotato fields was monitored to determine trends throughout the growing season. Low vector numbers were recorded through the entire season, consistent with previous research. Volatiles for infected and uninfected sweetpotato were collected to determine what effect virus infection has on volatile emission. Infected plants emitted a greater diversity of volatiles than uninfected plants. The effect of virus infection, as well as volatile compounds methyl jasmonate (MEJA), methyl salicylate (MESA), stylet oil and neem oil, with the potential to alter aphid behavior, were tested. Y-tube and settling assays were performed with green peach aphid (GPA) and cotton aphid (CA). GPA was more attracted to virus infected than uninfected plants, as well as plants and MESA odor. GPA was less attracted to plants and MEJA or neem oil odor than plants alone. Orientation towards volatile sources did not always correspond to settling preference as GPA preferred to settle on uninfected plants and plants treated with neem oil as well as MESA treated plants. CA did not orient towards volatiles or show any settling preference in any treatment. The electrical penetration graph technique (EPG) was performed to determine the effect of headspace volatiles from the four compounds on aphid feeding behavior related to virus transmission on infected and uninfected plants. In all treatments tested, headspace volatiles altered behavior related to virus transmission. However, headspace did not affect virus transmission rates in either aphid in virus transmission assays, suggesting that changes in aphid feeding behavior were not enough to alter transmission efficiency.
Dryburgh, John Lawrence, "Effects of Virus Infection and Volatiles on Aphid Virus Vector Behavior on Sweetpotato" (2019). LSU Doctoral Dissertations. 5008.
Available for download on Tuesday, June 23, 2020