Impacts of combining aphid and headworm management on natural enemy conservation and grain sorghum production

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 2-yr field study was conducted in grain sorghum to assess the impacts of an aphid resistant sorghum, 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 compared to managing each individually. 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.