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Now is the Time To Scout for Black Cutworms

Now is the Time To Scout for Black Cutworms
Don't rely on seed insecticide to prevent infestations in all cases.

The corn stubble field I walked through a few days ago was beginning to green up – not from cover corps, but from winter annuals. Purdue University Christian Krupke says fields like that might be prime candidates for black cutworm moths to lay eggs. The eggs will hatch into larvae that can cut plants if they grow large enough.

Pheromone trapping has caught a significant number of moths during recent warm spells, he says. The moths are coming up from the Gulf of Mexico where they overwinter. They can continue to come north until June.

Attractive to moths: Black cutworm moths might find this weedy growth attractive for laying eggs which could then attack corn seedlings if corn is planted into this field.

Moths that arrived very early likely laid eggs that perished due to cold weather. Moths arriving in the last few days, however, will lay eggs that will likely turn into larvae. One reason predictions form moth trap counts isn't an exact science is because they only catch male moths.

You can track the catch of moths at a location closes to you in the Purdue Extension Pest and Crop Newsletter. It's available online.

Black cutworms tend to appear in patches within fields. That's why Krupke suggests scouting as an economic approach rather than treating whole fields. Some hybrids do carry GMO traits which are effective against black cutworm.

Related: Early Black Cutworm Moths Killed; More Will Come

Insecticide-treated seed may also help on black cutworm control, depending upon the level of the active ingredient on the seed, but Krupke says they primarily suppress the smallest larvae during the seedling stage. It does little to control larger caterpillar-size cutworms that move over to corn after feeding on winter annual weeds, like chickweed or henbit. If there are dead or dying weeds in a field of young corn plants, there is that chance for black cutworm problems, Krupke notes. Besides, if the weather remains cool, uptake of the insecticide by the corn seedling is slower than normal.

He recommends scouting and using a foliar insecticide if necessary.

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