An outbreak of an invasive aphid was discovered damaging grain sorghum in Texas including Nueces County and neighboring states in 2013. The 2013 outbreak caused severe damage, with producers and crop consultants estimating 25-50% yield loss and total yield loss in some unprotected fields. According to work by Michael Brewer and Mo Way, with Texas A&M AgriLife Research Infestations were initially observed after sorghum heads were developing, but likely began infesting the crop earlier.
The aphid may be a new variant of sugarcane aphid, Melanaphis sacchari, that has a high preference for sorghum, or a very closely related species (M. sorghi). Infestations detected were very heavy, often with hundreds of sugarcane aphid per leaf. Leaves became sticky and shiny from honeydew and coated with sooty mold fungus (grows on honeydew) which hampered harvesting operations. Heavy sugarcane aphid populations and honeydew/sooty mold fields were observed in the lower Rio Grande Valley, the Gulf Coast, central Texas Blacklands, and northern counties bordering the Red River, as well as in southern Oklahoma along the Red River and from southwest to northeast Louisiana.
Fall populations on remnant sorghum of harvested fields and johnson grass have been detected in many of these counties, including Nueces County, positioning the aphid for possible outbreaks in 2014. Early insecticide trials conducted by Way, Brewer, and others have identified early management options. Natural enemies have also been observed feeding on sugarcane aphid. The effectiveness of 4 insecticidal treatments was compared to an untreated control on sugarcane aphids in a field in China, Texas. The field used for this work had been previously treated with Lorsban 4E 2-3 times but sugarcane aphid populations were still high at the time of application of test treatments. Insecticidal treatments included Lorsban Advance, Transform WG, Karate Z, and Dimethoate 4EC. All treatments provided a significant level of control compared to the untreated check except for Karate Z four days after treatment. More detailed information can be found in a recent poster presentation on the web at: http://ccag.tamu.edu/entomology/.
In light of the 2013 outbreak and observations of aphid fall populations, producers are being encouraged to thoroughly scout sorghum fields early in the growing season at least through early head development during the 2014 season to facilitate a timely insecticide application, should it be needed. While this aphids is of particular concern in 2014 growers should also be prepared for more common sorghum pests. Therefore, in addition to scouting entomologists also encourage sorghum produces to use systemic insecticide seed treatment or in-furrow insecticide, plant early to prevent midge problems, and use suggested insecticides for rice stink bug.
Individuals with disabilities, who require an auxiliary aid, service or accommodation in order to participate in any of the mentioned activities, are encouraged to contact the County Extension Office eight days before all programs for assistance. Extension programs serve people of all ages regardless of socioeconomic level, race, color, sex, religion, disability or national origin.