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Early Black Cutworm Moths Killed; More Will Come

Early Black Cutworm Moths Killed; More Will Come
Don't rely on seed treatments alone to ward off black cutworms.

Various cooperators trap moths and report the counts to Purdue University entomologists. Cooperators trap both black cutworm and armyworm moths. The moths typically ride breezes up from the Gulf Coast where they overwinter.

Counts were beginning to pick up and a sizable number of moths arrived at or before mid-April, notes John Obermeyer and Christian Krupke, Purdue entomologists. However, the pair says the harsh nights which followed wiped out most of those moths. If they were already laying eggs, it likely wiped out the eggs as well.

Black death: Left to its own black cutworm moths can cut off a sizable number of plants. (Photo courtesy John Obermeyer, Purdue University)

That's the good news, The bad news is that volunteers are still trapping because another batch of moths is likely to ride up on air currents soon. This means that the best way to handle black cutworm as far as a corn grower is concerned will be to scout fields and look for damage. If damage is occurring at or above the level that should pay for itself, consider applying a rescue treatment, Krupke says.

The problem with applying an insecticide just for black cutworm is that the insect often occurs in patches within a field, wherever the adult moth laid eggs. Spending money on an insecticide would not be a wise economic decision.

Related: 12 Pests To Watch For When Early Season Field Scouting

At the same time, don't think you're in the clear if you bought seed corn with the fungicide-protected coating on the seed, Obermeyer says. First, there are three levels of treatment – Poncho or Cruiser 250, 500 and 1,250. The lighter leaves have less killing power in the beginning.

While the treatment may knock out early germinating larvae, if plants are slightly older before bigger larvae attack, the control power of the seed treatment may already be gone, or greatly diminished. It's still why the entomologists believe the best policy is to scout cornfields, even if the seed was coated with a seed treatment.

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