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Protect Cotton and Soybean Crops from Hungry Insects

Protect Cotton and Soybean Crops from Hungry Insects

By Denise Attaway

Cotton and soybeans are popping up all across South Carolina and Clemson University Extension Service specialists say these major crops are susceptible to hungry insect pests.

Cotton insect report
Charles Davis, a Clemson Extension row crops agent in Richland County, said thrips – a tiny, destructive insect – are being reported in fields where cotton is emerging.

“Cotton is just going in the ground around here and we’re seeing something we wished we didn’t see,” Davis said. “I saw a recent video which showed thrips covering a white plastic pesticide container. So, I don’t doubt the danger of thrips is present. I’ve also seen a few grasshoppers along ditch banks looking for a meal now that the fields are crispy. Soon these ‘hoppers’ will be looking for some cotton to chew up.”

Jeremy Greene, an Extension and research entomologist and professor housed at Clemson’s Edisto Research and Education Center (REC), said the tobacco thrips is a frequent pest of seedling cotton that can reduce lint yield up to 50%.

Many at-plant treatments are providing protection, but some don’t look so good, he said. Plots treated with aldicarb look best. Neither pyrethroids nor Lorsban should be used for thrips control in emerged cotton.

“I don’t know if we’ll see the number of thrips get as high as it did last year,” Greene said. “But there are signs of injury in cotton planted in mid-April.”

Planting cotton in mid-April in South Carolina is a little early. Depending on the weather, cotton planting usually begins in late April and continues through the month of May in South Carolina, said Clemson Extension cotton specialist Michael Jones of the Pee Dee REC.

Planting later does seem to have benefits as research shows injury risk from thrips declines as the planting date is delayed. For early-planted cotton that is at highest risk, growers should consider using more effective at-plant insecticides that go in the furrow as an extra application (granular or liquid spray) with the seed and use seed treatments later in the planting window to reduce thrips risks. Insecticide treatments are important early-season to minimize yield loss and to ensure the crop isn’t delayed.

The thrips infestation predictor tool for cotton (TIP) advised cotton farmers not to plant early in the southern part of the state this year.

Grasshoppers are an issue right now and are best controlled when in the nymph stage, the entomologist said. Use Dimilin at a rate of 2 fluid ounces/acre to control nymphs. Pyrethroids and chlorpyrifos are good materials to use for adult grasshoppers, but controlling at the nymph stage is better as grasshoppers are difficult to control as adults, especially the big ones.

“Dimilin is a good choice to use proactively in fields where grasshoppers are expected to be a problem,” Greene said. “For farmers who are spraying emerged cotton and reacting to an insect problem, I would consider using a heavy rate of Orthene 97 for grasshopper adults and control of thrips.”

Other major pests of cotton are stink bugs, bollworm and tarnished plant bugs, but will be an issue later in the season

Soybean situation
About 6% of the state’s soybean crop had been planted as of May 8. In his test plot, Greene has some soybean plants that have emerged. No insects have found the plants – yet.

“We’ll likely see kudzu bugs and threecornered alfalfa hoppers pretty soon,” he said.

Kudzu bugs were the most common insect pest of soybeans in 2019. Pyrethroids provide excellent control of kudzu bugs. The same treatment for grasshoppers in cotton also applies to soybeans. Use Dimilin for nymphs and a pyrethroid for adults.

Podworm, stink bugs, soybean looper and velvetbean caterpillar are other insect pests of soybean that Greene warns farmers to keep a check on later in the season.

“Don’t forget to scout your crops early for insect problems,” Greene said.

Several online tools are available on www.clemson.edu/extension to provide farmers with pest control information. The Clemson Pest Management Handbook – 2020 has information to help control insect and weed pests. Free mobile apps, Calibrate My Sprayer and Mix My Sprayer, help with equipment calibrations and mixing pesticides.

Deer is another pest of soybeans. White-tailed deer cause millions of dollars in damage to South Carolina’s soybean fields each year. Greene has installed a fence on his test plot to help keep deer away.

To help South Carolina farmers stay ahead of pest threats, Greene is working with Syngenta to provide timely Pest Patrol Alerts. For information, go to https://bit.ly/SC_PestAlerts.

Economic impacts
Cotton and soybeans are important to the South Carolina economy. Information from the South Carolina Department of Agriculture shows cotton and soybeans are two of the top 10 commodities in South Carolina. Others are broilers, turkeys, greenhouse nurseries, corn, cattle, peanuts, eggs and wheat.

According to the United States Department of Agriculture National Agricultural Statistics Service, 320,000 acres of soybeans and 297,000 acres of cotton were harvested last year. Together, these crops brought in more than $217 million to South Carolina in 2019.

Source : clemson.edu