Impact of planting date and insecticide application methods on Melanaphis sorghi (Hemiptera: Aphididae) infestation and forage sorghum yield

Authors: UYI, OSARIYEKEMWEN - University Of Georgia; REAY-JONES, FRANCIS - Clemson University; Ni, Xinzhi; BUNTIN, DAVID - University Of Georgia; JACOBSON, ALANA - Auburn University; PUNNURI, SOMASHEKHAR - Fort Valley State University; TOEWS, M - University Of Georgia

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2022
Publication Date: 11/10/2022
Citation: Uyi, O., Reay-Jones, F.P., Ni, X., Buntin, D., Jacobson, A., Punnuri, S., Toews, M.D. 2022. Impact of planting date and insecticide application methods on Melanaphis sorghi (Hemiptera: Aphididae) infestation and forage sorghum yield. Insects. 13. Article 1038. https://doi.org/10.3390/insects13111038.
DOI: https://doi.org/10.3390/insects13111038

Interpretive Summary: Sugarcane aphid infestation remains a major threat to forage, silage, and biomass sorghum production in general across the southeastern USA. Studies on the management of this invasive pest are essential to developing or refining integrated pest management strategies against the sugarcane aphid. This study determined the impact of planting date and insecticide application on sugarcane aphid infestation and forage type (or silage) sorghum yield in Tifton, GA, and Florence, SC in 2020 and 2021. Early planted silage sorghum hybrid supported higher aphid density and more severe yield loss caused by aphid feeding damage in both locations. Yield results in Florence in 2020 showed that early planted sorghum suffered over 50% yield loss compared to late planted sorghum, while the applications of all three insecticide treatments resulted in significantly higher silage sorghum yield than untreated plots, where yield was reduced by 35%. These data indicate that early planting coupled with in-furrow insecticide application might be the most consistent way to suppress sugarcane aphid infestations and improve silage sorghum production efficiency in as an important forage crop in the southern US states.

Technical Abstract: Infestation of forage sorghum by Melanaphis sorghi remains a major threat to silage production in the southeastern USA. Studies on the management of this invasive pest are essential to developing or refining integrated pest management strategies against M. sorghi. The objective of this study was to determine the impact of planting date (early planting = mid-April to early May; late planting = late May to early June) and insecticide application (untreated, flupyradifurone in-furrow at 117 g/ha, flupyradifurone in-furrow at 146 g/ha, and flupyradifurone foliar at 73 g/ha) on M. sorghi infestation and forage sorghum yield in Tifton, Georgia, and Florence, South Carolina, USA, in 2020 and 2021. Early planted sorghum supported slightly higher aphid density and severity of infestation as evident in the greater cumulative insect days (CID) values in the early planted sorghum at both Florence and Tifton in 2020 and 2021. Our results demonstrate that a single foliar application reduced aphid infestations below the economic threshold level of 50 aphids per leaf. In contrast, in-furrow insecticidal application in selected plots at both locations across years significantly suppressed M. sorghi density to near zero levels throughout the growing season. Yield results in Florence in 2020 showed that early planted sorghum suffered over 50% yield loss compared to late planted sorghum, while the applications of all three insecticide treatments resulted in significantly higher forage sorghum yield than untreated plots. These data indicate that early planting coupled with in-furrow insecticide application may be the most consistent way to suppress M. sorghi infestations and improve silage production in forage sorghum in the USA.