Last summer I was called out to inspect some grain sorghum being produced by a rice farmer in Liberty County. We discovered a serious aphid problem on sorghum that was in the milk/dough stage of development. Most of the aphids were found on the underside of leaves. Virtually every leaf had hundreds of aphids sucking the plant juices out of the sorghum. Aphids are soft-bodied insects with piercing-sucking mouthparts. They excrete honeydew which is a sweet substance that causes foliage to appear glossy. Eventually, a sooty mold fungus grows on the honeydew causing the surface of the leaves to turn black. Not only were the aphids affecting yield, but the copious amounts of honeydew can hamper harvesting operations.
A colony of sugarcane/sorghum aphid on the underside of a sorghum leaf. Photo by Mo Way.
I was not sure of the identity of the aphid, so I sent preserved specimens to an aphid expert—Dr. David Voegtlin—at University of Illinois. David identified the aphid as the sugarcane/sorghum aphid which has been in SE Texas for quite some time, but for unknown reasons, developed high populations in 2013. I also observed similar damaging populations near China, TX in Jefferson Co., south of Meeker in Jefferson Co. and south of Stowell in Chambers Co. Thus, the infestations were widespread. Later, we found the aphid was reported damaging sorghum in Louisiana, the Lower Rio Grande Valley, and near Corpus Christi.
My project and Dr. Raul Villanueva at the Texas A&M AgriLife Research and Extension Center at Weslaco conducted insecticide evaluation experiments late last year. Basically, we found the best insecticide for managing this pest on grain sorghum was Transform WG. DOW’s new insecticide, with the active ingredient sulfoxaflor, has a unique mode of action and is applied as a foliar product to control sap-feeding insects. Currently, we are working with Drs. Mike Brewer, Gary Odvody, Charles Allen, David Kerns and the sorghum check-off board to obtain a Section 18 Emergency Exemption for this insecticide. We also are preparing grant proposals to obtain funding to conduct research to better understand the biology of this critter and develop an integrated pest management (IPM) program for this pest. Maybe this aphid will not be a problem next year or in future years, but we need to be prepared in case it continues to infest our sorghum fields. Seems like every year farmers are confronted with abnormal weather; exotic pests; market fluctuations; new regulatory policies and countless other obstacles to make farming challenging and difficult. This is why we must work together to address these challenges to keep U.S. agriculture competitive and vital.
