Foliar- and seed-applied insecticides for management of Melanaphis sorghi (Hemiptera: Aphididae) in Alabama

Authors: Pekarcik, Adrian; MENANYIH, SYLVESTER - Auburn University; JACOBSON, ALANA - Auburn University

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2023
Publication Date: 3/22/2024
Citation: Pekarcik, A.J., Menanyih, S.A., Jacobson, A.L. 2024. Foliar- and seed-applied insecticides for management of Melanaphis sorghi (Hemiptera: Aphididae) in Alabama. Journal of Entomological Science. 59(2):105-124. https://doi.org/10.18474/JES23-38.
DOI: https://doi.org/10.18474/JES23-38

Interpretive Summary: The sugarcane aphid, Melanaphis sorghi, was first identified as a new pest of sorghum in Texas in 2013 and was detected in Alabama by 2014. This pest feeds directly on the leaves, which reduces water and nutrient uptake by the plants, causing them to discolor and die. Once established, sugarcane aphid populations increase exponentially and can cause significant yield losses when left unmanaged. At the time of this study there was limited information on the effectiveness of chemical control options for M. sorghi on grain sorghum, and whether insecticides are compatible with natural enemies which prey on M. sorghi and suppress populations. Regional variation has been observed in other management tactics like host plant resistance and biological control. Thus, it is important to evaluate insecticides against M. sorghi in Alabama. The objective of this research was to evaluate the effectiveness of foliar-applied insecticides in response to active infestations, and insecticide seed treatments for early-season suppression of M. sorghi in grain sorghum in Alabama. A secondary objective was to identify natural enemy species of the aphid present in Alabama and determine whether their communities were influenced by insecticide treatments. Different seed treatments and foliar insecticides suppressed M. sorghi populations up to 47 days after application. Fifteen natural enemy species were identified in this study and their populations varied spatially and temporally. In general, natural enemy species richness was correlated with aphid abundance, regardless of treatment. The most effective insecticides should be compatible with biological control and integrated pest management programs. These results provide a foundation for the development of an integrated pest management plan for grain sorghum farmers in Alabama, in which the inclusion of host plant resistance and biological control could suppress M. sorghi population growth and ultimately reduce the need for insecticides.

Technical Abstract: Following the emergence of Melanaphis sorghi (Theobald) as a new pest of sorghum in the United States, research was conducted to identify tools and techniques successful at reducing populations and preventing economic losses in grain sorghum. The objective of this study was to assess the efficacy of seed- and foliar-applied insecticide treatments for management of M. sorghi. Small plot experiments were replicated at two locations to evaluate residual activity of neonicotinoid seed treatments, and foliar insecticides. Natural enemy presence was recorded in each of these trials to determine which predator and parasitoid species were using M. sorghi as prey. All seed treatments suppressed M. sorghi populations below a treatment threshold of 75 aphids per plant for 30% of plants for >6 weeks after planting. Foliar insecticides including flupyradifurone, sulfoxaflor, and thiamethoxam provided 3-4 weeks of population suppression, irrespective of M. sorghi pressure. Fifteen natural enemy species were identified in this study and community structure varied temporally and geographically. In general, natural enemy species richness was correlated with aphid abundance. We identified the most efficacious insecticides available for management of M. sorghi and determined that they should be compatible with biological control and integrated pest management programs.