Sugarcane aphids, Melanaphis sacchari, have been found this week (May 2019) on Johnsongrass in Montgomery County, Alabama. Johnsongrass was surveyed at multiple sites between Dothan and Auburn and only one site contained small populations of the aphids. Populations are currently low, ranging from 1-50 aphids per plant on Johnsongrass. These populations include nymphs, adults, and winged adults and have the capability to move to nearby sorghum.
When scouting for aphids, keep in mind that several different aphid species can occur on both Johnsongrass and sorghum. Sugarcane aphids have distinctive black-tipped antennae, tailpipes, and feet as shown in the above picture. A commonly co-occuring species, the yellow sugarcane aphid, Sipha flava, does not have the black-tipped appendages. Yellow sugarcane aphids are highlighter-yellow and hairy. Yellow sugarcane aphids rarely require treatment.
Scouting and Control
Sugarcane aphids populations can increase extremely quickly. Growers should take great care to scout their sorghum. Insecticidal seed treatments provide protection for approximately 30 days after planting. Producers should scout sorghum weekly for aphids. Once they are found in a field, increase scouting to twice-weekly. Producers can use the same thresholds for grain sorghum and forage sorghum. For sorghum from pre-boot to dough stage, 50 or more aphids per leaf on 25% of plants should trigger an insecticide application within 3 days at most.
This year in Alabama, producers can apply Sivanto Prime and Transform WG to grain and forage sorghum for sugarcane aphid control. Following an application, go back and check the field in 3 days to evaluate control.