Sugarcane aphids have a good chance of being a serious issue in Sorghum fields this year. Despite a slow start in 2015, the sugarcane aphid is now spreading fast. The aphid has been causing serious problems in Georgia where some farmers have been seeking insecticide alternatives after two applications of Transform, the allowable limit. This week, economically significant infestations were found as far north as Noble, Kay, and Grant Counties in Oklahoma, right on the Kansas state line. With some southerly wind, we will soon get winged aphids landing in Kansas sorghum.
Sugarcane aphids are small; light yellow to grey with dark cornicles (paired tailpipelike structures on the rear of the abdomen) that contrast with the remainder of the body. They are all female, and reproduce asexually. Adults give birth to live pregnant young nymphs. These young nymphs are mature and reproduce in 3 days’ time. They have the potential to kill seedlings, reduce seed numbers, but the most significant damage occurs as reduction in test weights. They also produce a copious amount of honeydew which can gum up machinery during harvest making it all but impossible to get the grain out of the field.
LSU AgCenter and Texas A&M Agrilife has set a preliminary threshold on boot/milk stage grain sorghum of 50 aphids per leaf colonizing 20 percent of plants in the field. With the aphids’ ability to reproduce so quickly, they can get past the threshold in a very short time, so scouting fields regularly is the best first line of defense. If it is determined that an insecticide is needed, Transform is the material of choice, preferably applied in a large volume of water (10-20 gal per acre). Sivanto is also approved, but it appears to require a higher rate to achieve similar results and ends up being considerably more expensive.
For more information about the sugarcane aphid, or if you think you have them in your field, contact your local Extension office.
Alicia Boor is the Agriculture and Natural Resources agent for Barton County K-State Research and Extension. You can contact her by e-mail at firstname.lastname@example.org or calling 620-793-1910