Several pests may reduce yield, and sorghum should be routinely scouted for insects and other problems. By planting grain sorghum in the recommended planting window, some insect problems can be reduced or avoided. Infestations of the sorghum midge, corn earworm, fall armyworm and sorghum webworm will typically cause more damage to late-planted sorghum. Fortunately, there are many insecticides that will control economically damaging populations of sorghum insect pests.
Common Insect Problems:
Sap-feeding Insects. Different types of aphids may be found on grain sorghum early in the season. These insects are found on top and underneath the leaves and whorls of sorghum plants, where they cause damage by sucking juices from the plant. The most common aphids found in grain sorghum are the sugarcane aphid, corn leaf aphid, and greenbug. The greenbug can be a serious pest or seedling plants, and the sugarcane aphid is a serious pest later in the season.
Insects Feeding on Grain Heads and Seed Kernels. The sorghum midge and sorghum webworm feed on the ripening grain kernels. Sorghum webworms feed on the ripening kernels by devouring the inside and leaving the hollow kernel shell. Corn earworms and fall armyworms usually consume the entire kernel as they feed.
Insects Feeding on Leaf Tissue. Corn earworms and fall armyworms feed in the whorls of young grain sorghum plants. Severe feeding injury to the growing point or intercalary meristem may destroy the emerging grain head.
Recommended Planting Dates:
Grain sorghum should be planted from May 1 to June 1 for highest yields. Planting before mid-May will avoid some insect damage from sorghum midge, fall armyworm, sorghum webworm and corn earworm.
Insecticide Seed Treatments:
Insecticide seed treatments such as Cruiser (thiamethoxam) and Poncho (clothianidin) are available from seed companies. Seed treatments will help control some seed and seedling pests such as chinch bug, greenbug, wireworms and white grubs. However, there has been little testing of these treatments in Tennessee. Recent data indicates that these insecticide seed treatments may reduce infestations of sugarcane aphid, which may be especially important on late-planted sorghum.
When Applying Insecticides: Read and follow label directions carefully before you buy, mix, apply, store or dispose of a pesticide. According to laws regulating pesticides, they must be used only as directed by the label. Alternate classes of insecticides when practical to minimize the chance of developing resistance. When pollinators are present, and especially when beehive are located near fields, apply pesticides in a way to minimize risks to bees and other non-target organisms.