Suppression of the sugarcane aphid, Melanaphis sacchari Zehntner (Hemiptera: Aphididae), by resident natural enemies on susceptible and resistant sorghum hybrids

Authors: FARIS, ASHLEIGH - TEXAS A&M UNIVERSITY; Elliott, Norman - Norm; BREWER, MICHAEL - TEXAS A&M UNIVERSITY

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2021
Publication Date: 4/1/2022
Citation: Faris, A.M., Elliott, N.C., Brewer, M.J. 2022. Suppression of the sugarcane aphid, Melanaphis sacchari Zehntner (Hemiptera: Aphididae), by resident natural enemies on susceptible and resistant sorghum hybrids. Environmental Entomology. 51(2):332-339. https://doi.org/10.1093/ee/nvab147.
DOI: https://doi.org/10.1093/ee/nvab147

Interpretive Summary: The sugarcane aphid, Melanaphis sorghi is an invasive sorghum pest that has spread to nineteen states in the U.S. and over 400 counties since 2013. It has threatened over 90% of North American sorghum production. Resident arthropod natural enemies such as 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 a natural enemy exclusion cage technique. 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 smaller-sized parasitoids), and complete exclusion (excludes parasitoids and predators), were used. Parasitoids were most abundant in the no exclusion treatment. Aphelinus nigritus Howard (Hymenoptera: Aphelinidae) (ca. 90% of specimens recovered) and Lysiphlebus testsaceipes (Cresson) (Hymenoptera: Braconidae) were detected in the partial exclusion treatment on both sugarcane aphid infested hybrids. Aphid suppression attributable to A. nigritus ranged from ca. 95% on the resistant hybrids and 80% on the susceptible hybrids when comparing aphid counts from the complete and partial exclusion treatments. In 2019, aphid suppression ranged from 47% on aphid-resistant hybrids and 6% on susceptible hybrids in south Texas and from 11% on aphid-resistant hybrids and 33% on susceptible hybrids in Oklahoma and was attributable to a combination of parasitism (A. nigritus) and predation by Scymnus spp. and Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), respectively. Our results supported that resident natural enemies contributed to sugarcane aphid suppression in aphid susceptible and partially aphid resistant. Aphelinus nigritus was a key contributor to suppression in south Texas and Oklahoma, while predation was substantial in Oklahoma. The significance of the results is documenting that natural enemies play an important role in suppressing sugarcane aphids in sorghum in the Southern Great Plains region.

Technical Abstract: 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 a 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 south Texas 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.