Insect pests add to problems for crop producers

COLUMBIA, Mo. – Crops, already stressed by drought and heat, are under attack by insects.

Producers need to scout for both the usual and unusual suspects.

“We do have several different treatments that take care of certain pests, but this year we have lots of pests that aren’t usually seen in this part of the world,” said Wayne Bailey, entomologist for University of Missouri Extension.

A leafhopper, normally found in Texas, went after Missouri wheat. The redheaded flea beetle is showing up on corn.

“They’re clipping silks on corn this year,” Bailey said. “That’s something I haven’t seen in my 28 years with the university.”

Typical pests are out there too. Japanese beetle numbers are high in some areas, Bailey said. They will go after both corn and soybeans. Spider mite numbers could explode because they love dry conditions, and we have lots of dry.

“What you’ll see is an off-color in the field, often in spots along the edges,” Bailey said. “In dry, dusty conditions their populations can double every seven to 10 days.”

Bailey said to take a white piece of paper into the field. Place the paper under a leaf and tap the top of the leaf. The spider mites will look like light brown, tan, yellowish or red dots crawling on the paper.

“If you have them, you need to do something pretty quick,” Bailey said.

If you have soybeans that are flowering, be on the lookout for the spotted cucumber beetle or the southern corn rootworm beetle, Bailey said. They’re the same insect, just two different names.

“It’s a yellow beetle with black spots and it’s feeding on soybean flowers,” Bailey said. “We’re seeing many more of them in soybean fields where they are either defoliating or going after flowers or both.”

Another problem is the striped blister beetle. Bailey said this beetle’s numbers tend to coincide with grasshopper populations. Last year we had high numbers of grasshoppers. It’s found on both soybeans and alfalfa, but it’s a severe problem in alfalfa.

“They can be in second- and third-cutting hay, and if a horse eats more than a hundred blister beetles it will kill the horse by sloughing off the intestinal tract,” Bailey said.

Horses exposed to a toxic number of blister beetles show an unusual symptom.

“They’ll blow bubbles in water tanks,” he said. “It’s a strange behavior, but it’s an early warning that they’ve eaten blister beetles.”

Blister beetles can be controlled, but use care because even dead, they’re still toxic, he said.

“Spray in the evening and hopefully any beetles on the alfalfa will drop to the ground. Then you can come through and pick up the hay without picking up the beetles,” Bailey said.

Bailey said he’s not surprised that some unusual insects are showing up. Agronomy practices, like seed treatments and breeding for specific pest control traits, can change the dynamic of crop pests.

“What we’ve seen in the last five years is that other pests that have been secondary, or maybe not a pest at all, are filling where we’re knocking out that major pest,” Bailey said.

Drought can also change the number and type of insects on crops.

“Certain insects like drought, others don’t, and those that benefit from drought often become a pest,” he said.

According to Bailey, producers need to be scouting to make sure there isn’t something out there eating the flowers, pods or ears of corn.

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Wayne Bailey will share his expertise at the MU Bradford Research Center pest management field day, July 12, starting at 8:30 a.m. For more information, see http://aes.missouri.edu/bradford.