Sugarcane aphid population densities have increased rapidly in Alabama sorghum fields during the first half of July. The aphid has been reported as far north as Colbert County, and damaging population densities have been reported as far north as Talladega County.
Growers should scout all of their sorghum fields to see if sugarcane aphids are above threshold. Populations build rapidly, so fields should be scouted twice a week once sugarcane aphids are found.
After a field is sprayed with an insecticide to control sugarcane aphid, it should be scouted again beginning about 4 days after application. Some sorghum fields in Alabama have already required a second application of insecticide to keep sugarcane aphid population densities below the action threshold.
Good spray coverage is essential for successful sugarcane aphid control, because it is hard to get the insecticide to penetrate through the sorghum canopy. Best coverage is achieved using high pressure,a nozzle designed to deliver a small droplet size, and at least 15 gallons of water per acre (gpa) when applied by ground, or 5 gpa by air.
The better the spray coverage, the longer aphid control lasts before another insecticide application is required. Sivanto and Transform insecticides shoud provide about 2 weeks of control between applications if they are applied correctly. Growers should rotate insecticides during the season. A reminder that the Section 18 label for Transform allows only two applications during the growing season.
Some early planted sorghum fields are approaching harvest. The presence of large numbers of sugarcane aphids and associated honeydew leads to problems with harvesting so scouting needs to continue as the sorghum heads are maturing. It is important to pay attention to preharvest intervals. Transform cannot be applied within 14 days of grain harvest or 7 days of forage harvest. Sivanto cannot be applied within 21 days of grain harvest or 7 days of forage harvest.
More information on sugarcane aphid in Alabama can be found in this publication: IPM Strategies for Managing Sugarcane Aphid in Alabama Sorghum