Sugarcane aphid: Beware of potential new pest of sorghum
Grain sorghum growers in Kansas need to be aware of a potential new pest this summer. The sugarcane aphid is a new aphid pest of sorghum that has been detected in 38 counties and counties of Texas, Louisiana, Oklahoma and Mississippi in 2013. Further expansion into other states is a possibility. This aphid can spread rapidly across a wide geographic range.
It is not yet confirmed present in Kansas, but is likely to arrive this summer, given the large populations of winged aphids flying in Texas right now, said J.P. Michaud, Kansas State University Research & Extension Entomologist at the Agricultural Research Center in Hays. The new aphid might be called the "white sugarcane aphid" to distinguish it from the yellow sugarcane aphid -- a completely different species. Discussions are ongoing with entomologists. Michaud warns this aphid feeds all the way up to seed fill in the pannicles and can reduce yield significantly, even if it doesn't kill younger plants.
"So we do want sorghum growers to be on the watch and report any suspect infestations," Michaud said.
In 2013, large populations of sugarcane aphids developed on sorghum in southern states. They produced large amounts of honeydew, in some cases choking combines and causing grain loss in northeast Texas and Louisiana. Growers lost up to 50 percent of grain sorghum yield in infested fields during 2013.
This insect appears to have changed its host from sugarcane to plants in the genus sorghum -- grain sorghum, forage sorghums, sorghum x sudan crosses and johnsongrass; or it might be a new introduced pest species according to entomologists at Texas A&M AgriLife Extension. Small colonies have infested corn plants, but they do not appear to feed well on corn, an entomologist at Texas A&M said.
The aphid is a key pest of sorghum and sugarcane in tropical and subtropical regions around the world, including Africa, Asia, Australia and Central and South America. Although it was reported in Hawaii in 1896, it first was found in the continental United States on sugarcane in Florida in 1977. It also was observed on sugarcane in Louisiana in 1999. These infestations broke out in summer and declined by winter. Neither introduction resulted in permanent infestation by the pest, an indication it was not, at that time, able to adapt to a more temperate environment.
Sugarcane aphids colonize the lower surfaces of lower leaves first and then advance to the upper leaves. In some situations if they are not controlled, the aphids even might colonize the grain sorghum head causing further damage and yield reduction.
When conditions are favorable, small colonies quickly can grow to large colonies and produce large amounts of sticky honeydew.
Aphid feeding causes yellow to red or brown leaf discolorations on both sides. The honeydew also might support the growth of black, sooty mold fungus. Infestations of seedlings can kill young grain sorghum plants; later infestations can prevent grain from forming properly or filling completely.
Natural enemies of sugarcane aphids include lady beetles, syrphid fly larvae, green lacewings and parasitic wasps. There is variation among sorghum lines in tolerance of sugarcane aphid feeding and research is ongoing to find resistant cultivars.
However, when populations of sugarcane aphids are increasing rapidly, insecticides might be needed to prevent yield losses and honeydew buildup before harvest according to entomologists at Texas A & M.
Sugarcane aphids are soft body insects that suck sap plant juices, can hinder plants growth and produce a large amount of honey dew. The sugarcane aphids seen in 2013 were gray to tan or light yellow. They are hairless as seen under a hand lens. The distinguishing feature of sugarcane aphids is their short, dark, paired, tailpipe-like structures called cornicles. Otherwise, only their tarsi (feet) are dark at high magnification.
They can reproduce rapidly with many generations during a growing season. As mentioned earlier, it has not been detected in Kansas, but with the high numbers in Texas, and Louisiana and with its detection in southeast Oklahoma, grain sorghum growers in Kansas need to be aware of this potential new pest to sorghum and be scouting their fields.
Stacy Campbell is agriculture Extension agent in Ellis County.