Aphid Parasitism: A Biocontrol Option against Aphid Pests of Pecan in the Southeastern US

• Main Author: Slusher, Eddie K
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2021
• Subjects: Agriculture; Entomology; Parasitology
• ISBN: 9798780623564

Three species of pecan aphid are important pests of pecans in Georgia. Growers often react to pecan aphid outbreaks by applying insecticides, which can lead to resistance development and detrimental non-target effects on natural enemies such as ladybeetles (Coleoptera: Coccinellidae), lacewings (Neuroptera: Chrysopidae), and Aphelinus perpallidus Gahan (Hymenoptera: Aphelinidae). Aphelinus perpallidus is a biocontrol agent of pecan aphids as it requires an aphid host in order to complete its life cycle. However, many portions of the ecology between pecan aphids and A. perpallidus are poorly understood. In the following studies we examined the effects of multiple abiotic and biotic factors on pecan aphids and A. perpallidus including seasonality, insecticide application, vertical stratification, and hyperparasitism. Through this research, it was found that pecan aphids are found in low numbers throughout the season in managed, commercial pecan orchards in Georgia but tend to follow the same seasonal trends as experimental orchards. A. perpallidus follows the same seasonal cycle as their hosts. Studies on the pecan aphid-parasitoid food-web, found five hyperparasitoid species associated with A. perpallidus in Georgia pecan orchards, one of the first times this had been analyzed genetically. It was also found that the insecticides flonicamid, sulfoxaflor, and afidopyropen managed pecan aphids while not being harmful to adult A. perpallidus and mummy abundance. Finally, studies on vertical stratification effects on aphids and A. perpallidus found that aphids, mummies, and adult A. perpallidus were predominantly found in higher abundance in the lower canopy of pecan trees. The results of these studies contribute valuable information to growers and interested parties on pecan aphid-parasitoid interactions.