Come Out Swinging

Cutworm damage

As most growers are well aware, the fight against early season insect pests begins well before planting. But once cotton does emerge, the timing of the first foliar application for insects can be crucial.

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It may seem like a paradox, but the first punch many growers throw in the fight against insects is actually a herbicide. By knocking down anything green in their fields prior to planting, growers destroy the shelter for unwanted insect pests.

“We feel like if we can keep that field weed-free for three weeks or more prior to planting, that pretty much eliminates the likelihood of having a cutworm infestation and it also helps you on some other things. It might help you, for example, on spider mite infestations early on in the season,” says Dr. Scott Stewart, Integrated Pest Management specialist with the University of Tennessee.

Though cutworms are only a sporadic problem in Stewart’s area of west Tennessee, they can be a real pain for those who have to deal with them. Starting with a clean slate is an excellent way to avoid having to deal with them post-emergence. But for those who are behind in their weed management, and have several weeds in their field close to planting, entomologists sometimes recommend spraying a pyrethroid insecticide near planting for cutworm control.

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An Emerging Foe
As the season progresses and cotton is reaching the one and two leaf stages, many growers around the Mid-South are forced to deal with increasing thrips pressure. Stewart estimates that over 90% of growers in his area are utilizing an insecticide seed treatment for this purpose – most often Aeris or Cruiser.

The alternative to a seed treatment, according to Stewart, is a granular in-furrow application of Temik. Practically no one goes unguarded against thrips. That would be a very risky proposition in the western Tennessee region.

“You don’t realize how big of a problem thrips are because you’re covering the problem up with these preventative treatments. But it’s a big one because it can really hurt yields. It can also delay the crop, which is a big deal for you if you’re in a northern environment like we are.

“We strongly recommend that people use some type of preventative treatment for thrips control. They’re just too potentially damaging,” says Stewart. Even if growers choose to use a preventative method for thrips control, foliar applications are sometimes necessary.

From the point of emergence on, the issue becomes timing. Once the cotton reaches the three-leaf stage, as long as it is healthy to that point, it becomes much more resilient against thrips. But if thrip pressure becomes a problem during those the first 21 days after emergence, a foliar application may be needed. Many growers opt to put down multiple foliar applications for thrips. Stewart believes that growers often create more problems than they solve with these multiple applications.

“The biggest mistake I see across the Belt is people will spray for thrips two or three times when only one spray was necessary. Or they’ll spray too late,” Stewart says.

“What a lot of people don’t realize is the best benefit from a foliar application comes when that application is made generally around the first or second true leaf of cotton growth. When that spray is made third or fourth leaf, a lot of times you’ve lost the benefit or some of the benefit, and you’re starting to create some potential problems with flaring aphids or spider mites.”

Stewart and his contemporaries have been working on a project to gauge the environmental conditions that would warrant a foliar application after the use of a seed treatment or Temik. The best case scenario for a grower, he says, is that his crop shoots up out of the ground and grows through the susceptible stage in a hurry.

“We do know if the cotton takes its time emerging and is growing slowly, those are scenarios where we’re more likely to see a benefit from foliar applications for thrips control,” he says.

“If we do need to make that application though, we need to do it and then get out early and leave it alone and not make two or three applications, because that really causes us some problems.”

The Looming Threat
For the past few growing seasons, the tarnished plant bug has wreaked havoc on growers around the Mid-South. While growers in Stewart’s area haven’t been affected as badly as those in areas like the Mississippi Delta, he believes his area could see significant plant bug activity again this year.

“They’re a problem for us. We don’t have the problems that they do in the Mississippi Delta, and there are a lot of places that can say that, but it’s still our number one pest. We’re probably making, in Tennessee, anywhere from two to five applications, depending on the year, for tarnished plant bugs.

“Based on what I’ve seen the last several years, there’s no reason to believe it’s not going to continue for a while,” says Stewart.
As the season progresses, plant bugs can appear as soon as cotton starts producing squares. Stewart says pressure varied in his area last year, with a few growers in southwest Tennessee seeing significant damage to plant bugs.

Stewart says Belay has shown promise on plant bugs, based on only a year of testing. He also says insecticides like Trimax and Centric have a good fit in plant bug management systems, especially during the early season. Other classes of insecticide are typically used later in the season. Stewart says he has high confidence in the recommended treatment thresholds for for plant bugs. The best thing growers can do for plant bugs, he says, is to be vigilant.

“It’s one pest that you really need to scout and pay a lot of attention to. They’re a challenging pest to manage when they occur in such high numbers, in part because they’re getting more resistant to some insecticides, but if you make the effort and the right decisions, you can manage them.”

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