University of Kentucky researchers are exploring alternative methods for controlling sugarcane aphid in sweet sorghum

University of Kentucky researchers are exploring alternative methods for controlling sugarcane aphid in sweet sorghum, a major crop for farmers in the state.

Through a Southern Sustainable Agriculture Research and Education (SSARE) On-Farm Research Grant, entomologist Nathan Mercer and his colleagues are studying a combination of parasitoids and insecticidal soaps as a pest management strategy to reduce chemical inputs, better manage yield loss and improve the overall sustainability of the crop.

Sugarcane aphid, a regularly occurring pest in grain sorghum, is relatively new to Kentucky sweet sorghum fields. The pest can significantly reduce yields via plant sap feeding, and sugary secretions that cause sooty mold on the plant leaves. Mercer said that many Kentucky farmers have ceased sweet sorghum production due to the level of losses causes by severe infestations.                     

“Tactics for managing sugarcane aphid on sweet sorghum are limited. The chemical used on grain sorghum requires an emergency use exemption label on sweet sorghum, and there are no organic insecticides available,” said Mercer. “Growers must rely on insecticidal soaps which are not always effective.”

In the two-year project (OS19-130), “Integration of Predator Releases with Insecticidal Soap Sprays for Management of the Sugarcane Aphid,” researchers are proposing combining insecticidal soaps with natural predators, mainly Aphidius colemani, a parasitoid wasp that specializes in attacking various aphid pests.

“The project initially called for using green lacewings, but the parasitoid is more host-specific and doesn’t disperse as far away from its host as green lacewings, so it’s a more targeted approach,” said Mercer.

Mercer said that he is hopeful a management strategy can be developed for farmers based on the project results, but the study is challenging.

“The main challenge with the parasitoids is the timing of their release with aphid infestations. Adult wasps only live for a few days,” said Mercer. “In addition, you need good contact with the insecticidal soaps for them to be effective, and aphids tend to hang out underneath plant leaves where it’s difficult to apply the product.”

Four Amish farmers from Hestand, KY are participating in the field trials, control fields only receiving insecticidal sprays as needed compared with field trials receiving the combination of the parasitoid releases and insecticidal soap applications.

The study is projected to be completed in spring of 2021.