Suppression of the Sugarcane Aphid, Melanaphis sacchari (Hemiptera: Aphididae), by Resident Natural Enemies on Susceptible and Resistant Sorghum Hybrids

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), is an invasive sorghum pest that has threatened over 90% of North American sorghum production. Resident parasitoids, coccinellids, syrphids, and lacewings prey on this aphid. Our objective was to compare and estimate parasitoid and predator suppression of sugarcane aphids placed on resistant and susceptible hybrids in a field setting using natural enemy exclusion cages. During 2018 and 2019 along the Texas Gulf Coast and Central Oklahoma, three natural enemy exclusion treatments-no exclusion (full access for parasitoids and predators), partial exclusion (access limited to parasitoids), and complete exclusion (excludes parasitoids and predators)-were used. The parasitoid Aphelinus nigritus Howard (Hymenoptera: Aphelinidae) accounted for 90% of recovered natural enemies. In 2018, aphid suppression attributable to A. nigritus was ca. 95% on the resistant hybrids and 80% on the susceptible hybrids when comparing aphid counts from complete and partial exclusion treatments, while few predators were observed. In 2019, aphid suppression was attributed to a combination of predation and parasitism. Relatively more predators were recorded at both sites, accounting for 14% to 33% of specimens recovered in the no exclusion treatment. Aphid suppression attributed to predators and parasitoids ranged from 85% on aphid-resistant hybrids and 27% on susceptible hybrids in southTexas and >95% on both hybrids in Oklahoma when comparing aphid abundance in the complete and no exclusion treatments. Parasitism and predation contributed to aphid regulation on both hybrids, which may accrue multiple benefits leading to a more resilient sugarcane aphid management system.