New pests relentless in march on crops

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WILMOT, Ohio – Like Sherman’s army on its march across Georgia, new pests are on an relentless march through farm country, finding new ways to destroy crops and destroy the producer’s profit margin.

According to Dr. Harold Willson, associate professor of entomology at Ohio State University, a new pest finds its way into Ohio about every ten years or so.

Willson chronicled for producers attending the regional agronomy meeting in Wilmot the story of their own Civil War.

The invasion of pests such the alfalfa beetle, Japanese beetle, and European corn borer, were followed by new pests such as the western corn rootworm and the cercal leaf beetle that invaded the state during the 1970s. The alfalfa blotch Ieafminer came in the 1980s, and the pest of the 1990s was the soybean cyst nematode.

With the new millennium will comes new pests, some that farmers already need to be on the lookout for in their fields, particularly their soybean fields, according to Willson.

The soybean aphid, commonly found in China, Japan, eastern Russia, Korea, Borneo, Malaya, Thailand, the Philippines, Indonesia, and Australia hadn’t been detected on this side of the Pacific until late last summer.

In August it began creating havoc in soybean fields in the Midwest. By October it had been identified in Ohio, Michigan. Indiana. Illinois, Iowa, Kentucky, Minnesota, and Wisconsin.

Pale aphids. Willson said the adult soybean aphid is about one millimeter in length and ranges in color from pale yellow to pale green. It reproduces quickly, producing between 10 and 15 generations in a season.

During the season, female soybean aphids give birth to live, mainly female, offspring. They are usually wingless, so they remain on a plant. building their numbers to the levels that will damage the field.

At the end of the summer, males develop and both the males and the females have wings. They fly to an over-wintering plant, where they mate and lay eggs to hatch the following spring – starting the process all over again,

Willson said if there is an aphid problem, producers will typically see a sticky honeydew on the leaves. Also infested foliage shows signs of cupping and yellowing, of stunted growth and loss of vigor.

And if this newest threat is not enough, Willson also cautioned producers to be aware that pests can change their behavior patterns.

For example, he said although the dark-sided cutworm is not a known pest to soybeans, it has been a problem with vegetables and field crops such as corn.

The Dark-sided cutworm has one generation a year, laying its eggs in the fall and hatching out the following spring.

Willson said cutworm larvae have a light brown head capsule and stripes similar to an army worm. Seedling injury occurs when the cutworm damages the plant at ground level or an inch or two above.

Corn rootworm is another pest presenting new challenges to producers and researchers alike, according to Willson.

“This pest is continuing to move east from Indiana and Illinois,” Willson said. “The question is whether the corn rootworm, is going to be a serious problem in Ohio. We think the numbers are leveling off in the first tier counties adjacent to the Indiana state line. We see an occasional flare-up, but not enough to see a real problem.”

Using the sticky trap method to determine the corn rootworm population in this area hasn’t been conclusive.

“We are getting a little higher catches,” he said. “But there are enough small fields and enough continuous corn that the traps aren’t reading the same, so it is harder to interpret.”

Ohio producers have also seen the damage that seedcorn maggots can do to their corn and soybean fields.

Willson explained that damage can be caused by a combination of things, including the late tillage of over-wintering weeds such as chickweed and henbit prior to planting, the coincidence of planting with peak egg laying activity by adult maggots, and delayed seedling emergence due to cool or wet growing conditions.


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