Little brown or green caterpillars could be gnawing their way through the kernels of a billion-dollar crop in Kentucky.
The University of Kentucky’s Integrated Pest Management Program has tracked a higher number of corn earworms than usual at the UK Research and Education Center in Princeton and Spindletop Farm in Lexington.
In a July 31 trap count, more than 200 corn earworms were recorded in Lexington and more than 100 in Princeton. Entomology in specialty crops extension specialist Julie Peterson said the trap in Lexington has caught the highest number of corn earworms in roughly 15 years.
“We have not seen numbers quite this high at this time of the year since like 2009 and 2010,” Peterson said. “This is looking like an unusually high flight of the moths, which could then lead to unusually high risk from those caterpillars in those vulnerable crops.”
Corn earworms eat corn, tomatoes, hemp and other crops. They’re also known as soybean pod worm, tomato fruit worm and cotton bull worm.
The moths largely migrate from Southern states to Kentucky as summer ends. It’s also possible for corn earworms to overwinter in the soil. As moths, they have yellow-ish brown wings.
Over the last five years, the average number of corn earworms at the end of July is about 50 per trap each week.
Peterson said lots of factors can influence the population and there’s a natural fluctuation year over year. Milder winters in the Southeastern U.S. means more moths survive and migrate to places like Kentucky, where conditions are prime for them to reproduce.
“Those eggs will hatch into caterpillars, and it's those caterpillars that are doing the feeding damage to the plants that we care about, and that's really where that injury is coming in, is very hungry, very voracious little caterpillars,” Peterson said.
The most serious economic injury from the earworms is to sweet corn and ears where the eggs are laid directly on the silks leading the caterpillars to munch on the developing kernels.
“They do really love sweet corn,” Peterson said. “The moths are very attracted to the fresh silks as they're being produced on sweet corn fields.”
The earliest sweet corn is showing up at farmers’ markets now, but any planted to be harvested a little later in the season will be silking at the start of August, Peterson said.
Farmers and backyard gardeners need to be on the lookout for this pest. Peterson said those with fewer crops can check for the tiny white eggs on the skills. For more commercial farmers, Peterson recommends using pheromone traps to see how many corn earworms are in the area.
The damage caused by earworms to the husk can also make it easier for other pests to access and damage the crop, Peterson said.
As for this season, it’s unclear what effects the spike in earworms will have. Corn is Kentucky’s top commodity. The cash receipts are valued at more than $1 billion.
“This trap in Lexington is good for awareness, but it doesn't necessarily give a farmer an idea of exactly what to do in their own field, exactly what are they finding in their own field,” Peterson said.
Those who see between five and 10 moths in a trap, should spray every five days, Peterson said. If you detect between 11 and 349, increase that to every four days. At 350 or higher, it’s recommended to spray every three days. There are a variety of management options available to farmers, but insecticides are the most popular approach.
