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Spider mites attacking row crops

By Staff | Jul 27, 2012

By Karen Schwaller


Extreme dry conditions in the state have growers not only scouting their fields for signs of drought stress, but also for possible infestations of spider mites in their soybeans.

“I’ve seen some spider mites around the Fostoria area, but by Friday (of this week) we may be seeing quite a bit more of them if it stays dry,” said Kurt Metzger, seed solutions specialist for Maxyield Cooperative.

Metzger said spider mites originally came in on the wind from the south. They suck the sap and juices out of the plant.

“The plants will turn a yellowish color” Metzger said. “You’ll see them around the edges of the field and around waterways first if they are there.”

Metzger said spider mites are so small that growers might need a magnifying glass to see them, but they could also shake the plant out on a white piece of paper, then watch to see if they are moving around.

Spider mites can reproduce very quickly.

“Their numbers can explode under the right conditions, in a matter of four or five days,” said Metzger. “They thrive in hot, dry conditions. If you start to see spider mites in your fields, don’t wait. You’ll want to do something about it now.”

Metzger said growers should be scouting soybeans and corn.

“Spider mites can also work on the lower leaves of corn plants,” he said. “By the time they hit the ear leaf, that’s when you’re going to want to have been treating for them.”

Metzger said growers should consult first with a local agronomist in order to identify the infestation and discuss options.

He recommends spraying with Lorsban or a generic Lorsban-type product, because other types of insecticides will not kill the mites.

“When you get to the Pocahontas and Fort Dodge areas, they have been spraying already,” Metzger said.

Peter Bixel, SciMax Team Leader for Maxyield Cooperative, said it pays to spray for them because a grower he knows realized a 17-bushel per acre yield reduction where he didn’t treat his crop.

With today’s commodity prices, he said, it’s kind of a no-brainer.

“You may have to spray for them more than once, though, because the spray won’t kill the eggs that are (hiding under) the leaves,” he said, urging growers to take necessary preventative measures to protect their crop.

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