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Western Farmer Stockman

In cotton: Entomologist: Be cautious in caterpillar control

High Plains cotton farmers may want to consider thresholds for caterpillars as moving targets this year.

“With cotton prices as low as they are and with production costs high, farmers will need to economize,” says Extension entomologist Jim Leser, who is with the Texas A&M Research and Extension Center in Lubbock.

“Thresholds are not set in stone, and this year those numbers represent a gray area,”

Leser says, “Currently, treatment triggers are set at 10,000 bollworms per acre. But with numbers at 10,200, the damage is not significantly different than at 8,000. We recommend that farmers not worry about infestations right around thresholds this year. Losses are not high enough to justify treatments.”

One exception is caterpillar populations that hang around the threshold for weeks. “Still, we recommend growers be conservative with treatments.”

Leser says farmers should watch high populations closely. “Often, we can find levels at threshold, but if we wait three days, populations are below the trigger point again.”

He says he would be reluctant to spray until populations reach 15,000 per acre throughout most of the season. “Economize but watch the cotton closely,” he says. “At 12,000 per acre, we lose only about $8 per acre.”

He says growers may want to wait until caterpillars reach at least one-fourth inch in length before spraying. “Allow natural enemies time to control them,” he says. “With good beneficial activity, populations may drop blow threshold level in three or four days. Weather also may take the pests out.”

Leser says observers are concerned with early beet armyworm infestations. “Some growers may have been justified in spraying early, if they had stands threatened and terminals were being damaged. But it is easy to spray twice before cotton begins blooming, and we can waste a lot of money treating too early.”

He says beet armyworm numbers have been extremely high early in the season in west Texas. “We picked them up in corn unusually early, and we've had reports of all kinds of armyworms, not just beets.”

He says seedling cotton does not provide an ideal host for beets but that cool weather may have reduced stress and allowed a good number to survive.

“Down the road, we're not certain what this early infestation will mean. Often we see high numbers early and then they fizzle. It's hard to predict.”

Again, he emphasizes watching the crop carefully and waiting until populations are above threshold levels before taking any action.

“Populations are unstable and changing,” he says. “Farmers or scouts may find high levels of beets, budworms or bollworms in only 15 percent of the field. We can't justify treating that. Often growers make emotional treatment decisions based on a small field sample.

“It's critical that growers keep track of the numbers. but it's also imperative that they don't concentrate just on the hotspots. That skews the results and may indicate that conditions are worse than they are.”

Leser suggests farmers or their scouts walk 50 paces without paying much attention to the plant conditions and selecting a plant at random to sample.

He hopes farmers have adequate beet armyworm control materials if conditions warrant treatments. He expects Denim Tracer and Steward to be available.

He says coverage with these new materials is critical. “With ground application, apply 10 gallons of material per acre. By air, if you don't use five gallons, you're wasting your time.”

He also recommends nozzles in ground rigs be lowered to get into the plants. “We see a lot of difference in control with over-the-top spray versus dropped nozzles.”

He says Tracer also works well but “performance drops if coverage is not adequate.”

He says cotton farmers should not use pyrethroids to control beet armyworms. “These materials do not provide adequate control,” he says. “And mixing pyrethroids with other materials is not necessary. Use the newer materials. Unfortunately, we do not have any cheap beet armyworm materials.”

Leser says Intrepid is not recommended for bollworm control “at the rates we use. We don't recommend it for mixed worm populations.”

It's a good beet armyworm material, however. “Intrepid is one of the least expensive beet armyworm materials we have, but growers should be aware of rotation restrictions. Current registration package allows for no rotation following use. That's a situation that probably will be cleared up, but restrictions now are rigid. However, I would not let that stop me from using Intrepid.”

Leser says low boll weevil numbers this year will mean lower treatment triggers for the Boll Weevil Foundation in active eradication zones. “But they will treat only 10 percent to 15 percent of an area with beet armyworm infestations. I was pleased with the success they had with that approach last year.”

Leser says bollworm numbers should be down this year. “I don't think they will be a major factor. Corn acreage is down significantly. I don't have a good feeling for loopers. They usually come in with beet armyworms. As with beets, I've seen high populations early fizzle out.”

Leser says farmers should try to avoid large losses this year and put up with some minor damage. He says being conservative with insect control will be especially important for dryland cotton.

“And, if growers do not have a consultant, they should check fields regularly for pests and other growth problems. Plant mapping offers an ideal opportunity to see what's in the field. It's one of the best things a grower can do.

“It doesn't cost a farmer anything to get in the field and look. And it may help him avoid some unpleasant surprises that costs a lot of money to correct.”


Editor's note: This is part seven of our Cotton 101 series, focused on producing the most efficient crop possible under challenging economic conditions. Subsequent articles will deal with late-season insect control.

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