Fall armyworm caterpillars are getting fat at the expense of farmers and homeowners in Illinois.
The pest is found in the Midwest nearly every year, but this year multiple generations came up from the southern states and Central and South America to mate and lay eggs.
“This just happens to be one of the worst outbreak years for the fall armyworm that we have seen in the eastern U.S. really in many, many years,” said Nick Seiter, University of Illinois Extension field cops entomologist.
The caterpillars appear brown, green or black in color, with light colored lines running along its back from head to tail.
They get the name “armyworm” because they march in large numbers before devouring a field in a few days. They are known to eat alfalfa, pastures, corn and small grains and can infest lawns and gardens. In hayfields or lawns, the affected area often appears as brown or burned out patches, resembling drought damage.
Seiter said the fact that the pests arrived late this year is good news for soybean growers.
“These insects do like to feed on tender, growing plant tissue, and a lot of our soybeans in Illinois right now are sort of past that point,” Seiter said.
It is a different story for double-crop soybeans that were planted following wheat. Those fields that were planted late are in particular peril.
Fall armyworm infestation is best controlled when the caterpillars are a half inch or smaller. Seiter said insecticide failure has been reported in parts of Illinois and in the south.
Illinois continues to lead the nation in soybean production, according to 2019 USDA estimates. Illinois soybean farmers raised over 532 million bushels of soybeans in 2019 on nearly 10 million harvested acres with an average yield of 54 bushels per acre.