Reciprocal effects of aphid and headworm management on the conservation of natural enemies and cultivation of grain sorghum in the southern United States

Authors: Elkins, Blake; Little, Nathan; Allen, Kerry; Portilla, Maribel

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sorghum is an important grain that is fed upon by many insect pests. One pest is a group of moth larvae, which consume developing grain in sorghum heads (headworms) and are typically controlled by spraying insecticides. The aphid Melanaphis sorghi (Theobald) is a more recent pest that feeds on sorghum leaves. Controlling this aphid generally utilizes a combination of plant defenses, insecticide sprays, and consumption by natural enemies. It is currently unclear if the management practices for M. sorghi or headworms interfere with the control of the other pest or natural enemies in sorghum. A two-year field study was conducted in grain sorghum to measure the impacts of sorghum plant defenses, insecticide sprays for M. sorghi, and insecticide sprays for headworms on pests, natural enemies, and sorghum cultivation in Mississippi. The results indicated that all management strategies could significantly reduce the number of pests without decreasing the relative amounts of natural enemies. No significant benefits were seen from combining the management of both pests. The yield and profit generated considering the cost of insect management indicated that the treatments applied for insect control were not worth their cost under the conditions observed during our study. This research demonstrated that there were no downsides to the management of one or both pests together, but it was not always worth it.

Technical Abstract: Grain sorghum (Sorghum bicolor L.) of the southern United States is attacked by numerous insect pests. These include lepidopteran larvae which infest sorghum heads (headworms) and have historically been managed by insecticide applications. The aphid pest Melanaphis sorghi (Theobald) has more recently emerged as an economic pest of sorghum leaves. Management for this aphid has included host plant resistance, insecticide applications, and suppression from insect natural enemies. It is currently unclear if the management practices for M. sorghi or headworms interferes with suppression of the other pest or natural enemies in sorghum. A two-year field study was conducted in grain sorghum to assess the impacts of an aphid resistant sorghum variety, insecticide applications for M. sorghi, and insecticide applications for headworms on pests, natural enemies, and sorghum cultivation in Mississippi. The results indicated that all management strategies could significantly reduce pest densities and conserve suppression from resident natural enemies. No significant benefits were identified from the combined management of both pests. The yield and economic returns from the insect control costs indicated that while pest densities were significantly reduced, other factors impacted sorghum production under the environmental conditions and pest pressures experienced during this study. This research demonstrated the feasibility of integrating multiple management tactics for aphids and headworms. This has the potential to enhance the efficiency and efficacy of sorghum integrated pest management, although it may not always be necessary.