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Don't Let Black Cutworm Catch You Off Guard

Don't Let Black Cutworm Catch You Off Guard
Two Purdue University extension entomologists say seed-coated insecticides don't guarantee control.

Two Purdue University Extension entomologists recently issued advice concerning black cutworm. As noted here a couple weeks ago, black cutworm moths have migrated into Indiana and have been found by reporters who use pheromone traps to catch moths. That means they are coming up from the southwest, because the moth does not over winter in Indiana.

Now the question for Purdue University Extension entomologists John Obermeyer and Christian Krupke: Should you treat for them before you plant or after you plant?

Cut plants: Black cutworm can cut plants and cause significant stand loss. Photo courtesy John Obermeyer, Purdue University Extension

Because the pest is sporadic and many factors determine if and when it will affect your field, the pair strongly believe the better approach is to scout your corn once it is up and apply foliar applications of insecticide if black cutworms reach economic threshold levels. Your county Extension educator should be able to help you in determining when that level is reached. It may depend some on the price of corn and size of the larva, and stage of feeding on your corn crop.

The University extension entomologists also caution that just because you're planting seed coated with an insecticide that should control black cutworm, you may not get total control. In fact, you may not get control depending upon the timing. The problem is that the insecticides on the side don't last forever, they note. Meanwhile, black cutworm moths don't invade all in one flush. They lay eggs over a period of time. It's possible that if the infestation is heavy enough, or if there are enough flushes of black cutworm moths that invade your fields, there still could be larvae hatching and ready to feed on corn plants after the insecticide wears off.

Some of this will depend upon when corn is planted and weather conditions between now and then. They strongly urge scouting no matter whether you applied an insecticide or not.

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