Recently, David Kerns and I have been receiving more calls about aphids in grain sorghum. Three species of aphids colonize grain sorghum in Louisiana – corn leaf aphid, yellow sugarcane aphid and green bug.
The corn leaf aphid is blue to grayish green in color with black cornicles (twin exhaust pipes on rear of the body). Corn leaf aphids are typically found in the whorl, and development occurs sporadically throughout the growing season. Large populations can develop on larger plants; however, their effects on the crop are often negligible. As a general practice, control of corn leaf aphid is not recommended because this insect is seldom an economic pest.
The yellow sugarcane aphid has a lemon yellow body with a double row of dark spots down the back and is covered with small spines. Yellow sugarcane aphids will occasionally infest grain sorghum and can cause an issue due to the injection of a toxin when feeding. Areas of intense feeding will often result in purpling of young plants or chlorotic discoloration in older plants. Yield losses are most likely to occur in seedling infestations of this insect, but high numbers infesting older sorghum shouldn’t be ignored.
The green bug has a bright lime green body with a dark green stripe running down the middle of the back and cornicles with black tips at the end. Green bugs typically congregate on the underside of fully expanded leaves, and infestations are rare in Louisiana. This insect is a serious threat to grain sorghum because it will inject a toxin while feeding. Large numbers are capable of reducing yields and in extreme cases will cause plant mortality. If a green bug population does develop, consider the size of the plants, growing conditions, crop maturity and presence of beneficial insects when determining if an application is warranted. Applications may be justified when larger to preboot stage sorghum is exhibiting symptoms of red spotting or yellowing of leaves prior to leaf death. In preboot to mature sorghum, an application may be justified when green bugs cause desiccation of more than two of the lowest fully expanded leaves.
For more information or if you have any questions or concerns, please contact:
Sebe Brown at 318-498-1283 (cell) or 318-435-2903 (office)
Dr. David Kerns at 318-439-4844 (cell) or 318-435-2157 (office)
Dr. Julien Beuzelin at 337-501-7087 (cell) or 318-473-6523 (office)