Influence of Temperature on the Efficacy of Foliar Insecticide Sprays Against Sugarcane Aphid (Hemiptera: Aphididae) Populations in Grain Sorghum.

The use of foliar insecticide sprays at low temperatures may result in decreased efficacy in grain sorghum, Sorghum bicolor L. Moench, for control of sugarcane aphid, Melanaphis sacchari (Zehntner). Sulfoxaflor and flupyradifurone were evaluated to determine the impact of temperature on their efficacy against sugarcane aphid in grain sorghum. Sorghum was treated at the soft dough growth stage with sulfoxaflor and flupyradifurone, as well as an untreated check. Leaf discs were pulled at various intervals from 0 to 10 d after treatment, placed in water agar plates, infested with aphids, placed in growth chambers at 15.5°C or 29.4°C, and evaluated 48 h after each interval. In 2015, both insecticides resulted in similar levels of sugarcane aphid mortality and efficacy decreased at a similar rate at 15.5°C. At 29.0°C, flupyradifurone resulted in greater mortality of sugarcane aphid than sulfoxaflor as length of time after treatment increased, suggesting that it provides longer residual control than sulfoxaflor. In 2016, both insecticides provided poor control of sugarcane aphid at 15.5°C for all time intervals. At 29.0°C, flupyradifurone provided overall better control than sulfoxaflor. These data suggest that lower temperatures can reduce the efficacy of both sulfoxaflor and flupyradifurone. In addition, flupyradifurone appeared to provide longer residual control and overall better control of sugarcane aphid than sulfoxaflor. If lower temperatures occur when sugarcane aphid populations exceed current thresholds, weather forecast should be considered in pest management decision-making process.