Mild winter may increase insect, weed pressures

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Crop pests may be more abundant in Indiana farm fields this spring because of what continues to be a mild winter.

Some species of insects and weeds may have benefitted from the warmer-than-normal temperatures and lack of snowfall in the state, two Purdue Extension specialists say.

"We have two groups of insects in Indiana - those that migrate here and those that overwinter here," said entomologist Christian Krupke. "Those that overwinter here as adults, above or close to ground level, have had a particularly favorable winter so far."

Some of those insects are corn flea beetles, alfalfa weevils and bean leaf beetles.

"Last fall, we had our highest population of bean leaf beetle in quite some time. Because there should be good overwintering survival, I think we could see high spring populations this year, as well," Krupke said.

The good news for farmers is that virtually all corn and most soybean seed is treated with insecticide, so any protection available is already on the seed. According to Krupke, that means there is little more for growers to do at this point.

Because seed treatments vary in the amount of protection they provide against different pests, Krupke said producers need to keep an eye on their crops as the growing season progresses and apply any necessary foliar insecticide treatments if feeding is severe.

Weeds, on the other hand, could be a more visible problem for grain farmers this spring. Indiana has had enough warm days for winter annuals to germinate, said weed scientist Bill Johnson. Although those weeds go dormant in below-freezing temperatures, warm weather promotes their growth.

"When winter annuals have had a lot of growth, soils dry and warm more slowly in the spring because of the weed cover," Johnson said. "It's much harder for farmers to get sprayers out for burndown treatments on cold, wet soils."

A delay in burndown can lead to a delay in planting, but spraying on wet soils can result in ruts. If weeds aren't treated early enough in the spring, they may become too large to control with herbicides.

Some of the weeds most likely to cause problems are henbit, chickweed, purple deadnettle, marestail, annual bluegrass, Carolina foxtail and downy brome.

"Growers need to assess weed size, and if the fields are dry enough in March, they need to get burndown treatments and residual herbicides on their fields earlier than normal," Johnson said.

He recommended glyphosate- or gramoxone-based burndown treatments with residual herbicides added to them.

As planting season approaches, both Krupke and Johnson will provide insect and weed updates via Purdue Extension's Pest and Crop Newsletter at

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ky  |  February, 20, 2012 at 07:53 PM

24-d or glyphosate work well at above freezing temps ,as annuals are growing and translocating. Eradicating now should control any until summer annuals appear

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