Growers have been reporting greenbugs in sorghum and corn leaf aphids on corn in south central Nebraska, according to Bob Wright, UNL Extension entomologist.
Greenbugs should be monitored closely for the next couple of weeks in case economically damaging populations develop. Predator populations, particularly lady beetles and greenbug parasites, may be found in many fields. The greenbug parasite is highly effective in controlling greenbugs if it gets started early, he says.
The adult parasite is a small wasp that lays eggs inside greenbugs. The immature stage (larva) of the parasite develops internally and ultimately kills the greenbug. Just before completing development, the larva causes the greenbug exoskeleton to swell and change to a tan color. This is the parasite pupal stage, called a mummy. The wasp will emerge from the mummy in one to two days.
Because parasites and predators can be highly effective in controlling greenbugs, Wright recommends delaying use of insecticides until economic thresholds are reached.
Most insecticides registered for greenbug control usually provide excellent control. Insecticide-resistant greenbugs have occasionally been present in Nebraska, but there have not been any recent reports of insecticide failure in Nebraska.
For more information on greenbug management refer to the UNL Extension NebGuide Management of Greenbugs in Sorghum (G838). It can be found at www.ianrpubs/unl.edu/sendit/ec130.pdf.