By Nick Seiter, Extension Entomologist
Last week, we found very small colonies of sugarcane aphid in johnsongrass in Ashley County. This is similar to the limited population development that was occurring at this time of the year in 2015. While we have not yet found them further north this season (and there have been no reports of the aphid in seedling sorghum in Arkansas), it is a good time to start thinking about sugarcane aphid management in grain sorghum for the coming season.
We have been granted a Section 18 emergency exemption for the use of Transform WG in grain sorghum to control sugarcane aphid again in 2016. (For further details, see a recent blog post by Dr. Gus Lorenz). Along with Sivanto, this gives us two chemistries that we can use for sugarcane aphid control in sorghum. Last year was our first experience with Sivanto in the field, and we were generally pleased with its performance; initial control was good, and residual activity in most cases was stronger than Transform down to the 4 oz./acre minimum on the label. The use rates for Transform WG under the Section 18 exemption are 0.75-1.5 oz./acre, and the rates for Sivanto under a 2(ee) recommendation are 4.0-7.0 oz./acre.
A new feature of the Section 18 exemption for Transform in 2016 is a restriction on applications during bloom, which is unfortunately when sugarcane aphid infestations tend to “blow up” in most fields. Sivanto will be the only legal option for sugarcane aphids during this period. Although most infestations in the past have not occurred until bloom or later, severe infestations during boot have been devastating where they have occurred, and infestations during harvest can lead to mechanical issues and reduced harvest efficiency. It pays to be vigilant for this pest throughout the growing season. We will continue to send out updates on the situation as the aphid moves throughout the state.