Impact of planting date, host-plant resistance and insecticide applications on Melanaphis sorghi and grain sorghum yield

Melanaphis sorghi, commonly known as the sorghum aphid, is a significant pest of sorghum production across the southern USA. As integrating control methods are critical in managing this pest, we investigated the impact of planting date, host plant resistance and insecticide application methods on M. sorghi and grain sorghum yield at Tifton, Georgia (31.5120° N, 83.6434° W). Field experiments with two planting dates (mid-April to early May; late May to early June), two sorghum cultivars (resistant cultivar: DKS37-07 and susceptible cultivar: DKS53-53) and three insecticide treatments (untreated control, flupyradifurone in-furrow at 117 g/ha, and flupyradifurone foliar at 73 g/ha) were conducted on grain sorghum in the spring/summer of 2022. Early planting supported higher aphid density and severity of infestation (cumulative insect days [CID]) on both the susceptible and resistant cultivars. Aphid density and severity of infestation on the susceptible sorghum cultivar (DKS53-53) were 25% greater than on the resistant cultivar (DKS37-07) for both early and late planted sorghum. While a single foliar application significantly reduced infestations below the economic threshold across all treatment combinations, in-furrow insecticide application was the most effective, suppressing aphid population to a near zero infestation. Although planting resistant cultivar was not associated with improved sorghum yield, early planting and in-furrow insecticide application significantly preserved grain yield. The study suggests that combining early planting, resistant sorghum cultivars and in-furrow (IF) can synergistically suppress M. sorghi infestations and improve grain yield in sorghum production in southern USA.