This past week, sugarcane aphid was detected and confirmed infesting sweet sorghum in Monroe County. The next day, we detected it in Fayette County on sweet sorghum as well. These are the first confirmed detections of 2017 and are a bit earlier than 2016 reports. Sugarcane aphid is a very serious invasive pest of grain, forage, and sweet sorghum, and this represents the third year we have found it in Kentucky. This pest can build up to heavy infestations very quickly and will greatly weaken or kill plants through excessive removal of plant sap with its piercing-sucking mouthparts.
Grain, forage, and sweet sorghum producers are advised to scout their fields on a weekly basis by examining the undersides of leaves for sugarcane aphid. At a minimum, producers should examine at least 40 leaves in small-acreage fields. The action threshold for treatment that we are using was derived from grain sorghum in Texas and is approximately an average of 35 aphids per leaf. This aphid has the ability to increase in number very quickly, so if these aphids are detected in a field, but are below threshold, the field should be rechecked in a few days.
This year we would like to track the progress of sugarcane aphid and would like to get reports of infestations on a county by county basis. Sugarcane aphid in the previous 2 years did not infest the entire state.
Emergency Specific Exemption for Sivanto Prime
The EPA granted a specific exemption for Sivanto Prime use against sugarcane aphid on sweet sorghum in Kentucky in June and the section 18 label was issued last week. The exemption lasts until November 15 of this year and allows up to 4 foliar applications, with a rate of 4 to 10.5 fluid ounces per acre, and a maximum seasonal use of 28 fluid ounces per acre. Applicators must be in possession of the section 18 labeling for Kentucky and be certified applicators. This year, to meet EPA requirements for reporting, we need applicators to notify David Wayne through email (David.Wayne@ky.gov) at the Kentucky Department of Agriculture (KDA) with acreage treated and amount of Sivanto Prime used. This will help to ensure we are eligible for future Environmental Protection Agency (EPA) exemptions.
Grain and Forage Sorghum
Sivanto prime can be used in grain and forage sorghum also. However, there are some considerations when this product is used in grain and forage sorghum. These are:
- Sivanto Prime can be used at a rate of 4 to 7 fluid ounces per acre; the maximum allowed per year is 28.0 fluid ounces per acre
- There is a 21-day pre-harvest interval for dried grain, stover, or straw; and a 7-day pre-harvest interval for forage sorghum, and
- There is a 7-day minimum interval between applications for forage or grain sorghum.
By Raul Villanueva and Ric Bessin, Extension Entomologists