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Mild Winter = Pest Pressure

Mother Nature didn’t do us any favors with a mild winter.

It was a relatively mild winter throughout the Midwest. Overwintering insects had favorable odds of survival, says Erin Hodgson, Iowa State University Extension entomologist. “We didn’t have exceptional cold snaps,” says Hodgson.

Since Mother Nature didn't do us any favors in pest control, a lot of insects on the edge of surviving had a pretty good chance.

It’s not just the overwintering pests you have to be concerned with this year. “Some of the more Southern insects – black cutworm and armyworm – have started migrating earlier in the year than when they normally would,” she says.

Managing for pests

There are still areas throughout the Midwest where soils are warming up slowly. Planting should be based on the soil temperatures, says Hodgson.

“Warm soil temperatures, above 50°F., allow for vigorous vegetative growth, which helps the plant to outpace the pest,” explains Hodgson. “If the seed is sitting in the ground and not germinating because the soil is cold, it gives maggots, slugs, and other pests the chance to cause stand loss because the plant is growing slowly.”

Scouting will be a worthwhile investment

If you planted cover crops this year, leave enough time between the termination and planting of your row crop.

“You don’t want to have any green cover crop when corn comes out of the ground,” says Hodgson. “The longer the window you can have between termination and planting the better.”

Cover crops can act as a “green bridge” by providing food for the pests until the row crops emerge, says Hodgson.

“Both black cutworm and army worm are very mobile,” she explains. “They will move very quickly from field to field to find food.”

Waiting until the cover crop has died before planting will reduce the odds of damage from these pests. Weeds can also act as a green bridge and should be managed accordingly, says Hodgson.

Scout pasture or CRP ground transitioning back to corn or soybeans first. “Those areas harbor pests like grubs,” says Hodgson. “That transitional land deserves a little more attention.”

After planting, conduct seed checks to see how germination and growth is progressing.

“Insects are nocturnal,” says Hodgson. “You won’t see them during the day. Instead, you have to look for the signs of feeding and not the insects themselves.”

Scout for the following:

  • Seeds germinating
  • Damage to the seed or seedling
  • Missing plants (not due to planter skips)
  • Once emerged, watch for defoliation

In some cases, it’s a replant situation if it’s caught too late, she says.

Worried about diseases from cover crops? Alison Robertson, Iowa State University Extension plant pathologist, found if you have a short interval between killing rye and planting corn, you increase the risk of getting disease. If you can terminate 10 to 14 days before planting, then you will have a reduced chance of yield loss.

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