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Worms (and rain) in the Indiana, Ohio forecast
 
By Doug Graves
Ohio Correspondent

LAFAYETTE, Ind. – April showers bring May….worms?
Indeed. At least entomologists in the Eastern Corn Belt are warning growers to be alert for black cutworm and armyworm infestations in corn, soybean and wheat fields as soon as mid-May, based on high moth counts in some Midwest states.
“Cutworm moths arrived early in the Midwest this year,” said DTN entomologist Dr. Scott Williams. “Both cutworm and armyworm moths are snowbirds. They don’t much care for Midwest winters and spend the coldest months in southern states, all the way down to the Gulf. They rely on spring storm systems to migrate back up into the Midwest each year.”
Entomologists in the tri-state region of Ohio, Indiana and Kentucky have been on the lookout for these pests.
“We’ve been collecting these pests in our expanded trapping this year,” said Andy Michel, associate professor of entomology and associate director for the Center for Applied Plant Sciences at The Ohio State University. “The true armyworms feed on wheat before moving on young, late-planted corn. Black cutworm can feed on young corn and even completely cut plants. The moths of these pests migrate from the south and lay eggs in April and May.”
True armyworms prefer to lay eggs in wheat and even grassy cover crops like rye whereas black cutworms tend to lay eggs in weedy fields, especially those with chickweed or purple deadnettle. “Infestations are really hard to predict, and the best way to prevent damage is by scouting,” Michel said.
While Indiana, Ohio and Kentucky have been inundated by rains the past few weeks, precipitation is not the root cause for the influx in these pests.
“The likelihood of black cutworm being a problem is not really a function of rain, but more of the weather fronts that may or may not have brought cutworm adult moths with them earlier this year,” said Christian Krupke, field crops extension entomologist at Purdue University. “We are past the big influx of adult moths at this point. The prior trap captures indicate that we may have some high pressure in parts of the state.”
According to Krupke, the freezing temperatures (and snow) in mid-April spurred an increase in the black cutworm and armyworm moth activity.
“The dramatic swings in temperatures we’ve had are an annoyance to us, but to an insect dependent on heat accumulations for development, it may be the difference between minor damage to a wide-spread outbreak,” he said. “In other words, egg-laying and hatching of these pests may have occurred, but it will be a couple of weeks before we know the full extent of this year’s threat to our row and small grain crops. This is why we monitor for moth arrival, and intensity of captures, coupled with temperatures to track their development.
“Black cutworms feed on many host plants, including a broad range of weeds. They are perfectly happy without corn, although cool temperatures and slow-growing plants increase the risk. Along with high trap captures, weedy fields, especially chickweed, are the areas to prioritize with scouting. The younger the plants, the more vulnerable they are to cutting. Leaf notching damage can be caused by earlier instars of cutworms and are not as much of a concern. Cut plants are evidence of large larvae in the field.”
A single black cutworm larva is capable of cutting approximately four corn plants during its lifetime, depending on the size of the plants. They are especially attracted to chickweed. Black cutworms sometimes drag cut plants under dirt clods or into small holes in the soil to continue their feeding. They usually feed at night or during overcast days.
Female armyworms lay eggs in grasses including wheat, where eggs hatch over two weeks. As the larvae grow, they can defoliate wheat plants and lead to yield loss. Armyworms can also cause damage to corn that is planted into wheat fields or other fields that have a grassy cover.
“There is a variety of insecticides out there and we don’t recommend any particular product,” Krupke said. “The key action for producers and consultants to take is scouting of vulnerable fields. Insecticidal seed treatments should not be relied upon for control, especially now that many fields have had so much rainfall. For scouting corn seedlings, look for notches showing leaf feeding and then dig around the base of the plants to confirm that the pest in present and feeding on the crop. Don’t wait for cut plants to act. Those larger larvae are harder to kill and cut plants obviously cannot recover. The damage is already done at that point.”
5/17/2021