Dr. Maria Balota confirmed that sugarcane aphid has been found in a sorghum field in Isle of Wight County, Virginia. Dr. Ames Herbert confirmed it in sorghum at the Tidewater AREC in Suffolk on September 17. Due to the ability of winged aphids to spread rapidly and their high reproductive potential, we strongly recommend that all Virginia sorghum be scouted for this pest.
All sorghum should be considered vulnerable to this pest until harvest. Accumulated aphids and honeydew have the potential to create mechanical harvest problems (i.e., stopping up combines) in full-season sorghum this season. Additionally, double-crop sorghum (which could be harvested into November) and forage sorghum are at risk to both yield loss due to sugarcane aphid feeding and mechanical harvest issues.
Please let Dr. Herbert (firstname.lastname@example.org) or Dr. Balota (email@example.com) know if additional sugarcane aphid infestations are found in Virginia sorghum, so that we can track this pest for future program development.
There are several other aphid species that can infest sorghum but sugarcane aphid can be differentiated from the others being smooth, cream yellow, with two, short dark cornicles (“tailpipes”) on the hind end (Fig. 1). Fig. 1. Aphid species occurring on sorghum.
Scouting and thresholds
We recommend that all sorghum be scouted for sugarcane aphid. Lower leaves should be lifted up so that they can be examined (Fig. 2). Research by Mike Brewer, Texes AgriLife, and David Kerns, LSU, has provided the most up-to-date Econominc Injury Level (EIL) of 50 to 125 aphids per leaf at sorghum prices of $4/bu; and the currently recommended Economic Threshold (when the insecticide needs to be applied to prevent the population from reaching the EIL) of 25 – 30% infested plants with 50 aphids per leaf.
As Dr. Ames Herbert mentioned in an earlier Virginia Ag Pest and Crop Advisory, we have pursued a Section 18 Emergency Exemption for the use of Transform (sulfoxaflor) insecticide. This process involved cooperation by VDACS who put the request together and forwarded it to the EPA. We are awaiting approval.
Having Transform would give us access to the two insecticides that most other states are relying on to combat sugarcane aphid–Transform and Sivanto. Sivanto is currently labeled for use in Virginia sorghum, and there is a Section 2(ee) Recommendation for use of the lower (but still effective) rate of 4-7 oz/A. Since controlling heavy infestations may require two applications, having these options provides insecticides with different chemistries–always a good strategy.
Additional information and images You may want to see Angus Catchot’s comments on Mississippi State’s website. Please refer to the section “Harvest Aids and Sugarcane Aphids” but note that as of Sep. 18, 2015, Virginia does not have the Transform option.