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Tarnished-Plant-Bug-Adult-UTIA-Stewart.jpg Scott Stewart/UTIA

Squaring off with plant bugs and other early-season cotton pests

University entomologists offer several considerations for getting the drop on early-season cotton pests.

You know they’re coming: plant bugs, thrips, and their posses. University entomologists offer several considerations for getting the drop on these early-season pests.

University of Tennessee Entomologist Scott Stewart says, “Most of the state’s cotton growers plant insecticide-treated seed, with imidacloprid being the base treatment. Growers can also use an in-furrow insecticide application; granular materials include AgLogic 15G (aldicarb), especially in fields with substantial nematode problems, in addition to thrips, and liquid materials include imidacloprid and acephate.”

Plant bugs remain the Mid-South’s No. 1 insect pest. “Early-season, we still have neonic products such as Centric and imidacloprid,” Stewart says. “I think they are options for the first spray or two prior to flowering, but as we get closer to bloom, we probably will use them in combination with other materials, such as Diamond.

“All the Mid-South states will have another Section 18 label for Transform, which has been an excellent product for us; we’re using more of it than before. In the middle of the season, once we get into bloom, we consistently use three products: Transform, Orthene, and Diamond.

“I like mixes such as Transform + Orthene or Diamond + Orthene. Transform stands very well on its own, but I like mixing it, particularly late in the season, with something like Bidrin or Orthene to catch stinkbugs. However, you can often accomplish the same thing by rotation.

“Of course, insecticide selection depends on what’s occurring in the field. The important thing is to use different modes of action for broader control and resistance management.”

STACK YOUR TREATMENTS

Clemson University Entomologist Jeremy Greene says thrips are South Carolina’s most predictable insect pests in cotton every year so he urges growers to plan on using preventive treatments. Most cotton seed comes with treatments that help control thrips.

“We have other options, too, including in-furrow applications; we sometimes combine seed treatments and an in-furrow application. If you have a large acreage and you have to spread planting out for a month or longer, it might be a good idea to stack your treatments on some of the earlier crop that will be more susceptible to thrips because of the cooler temperatures that slow plant growth. And on later planting dates, you can just go with the seed treatment.

Applications of in-furrow insecticide include granular and liquid formulations. “Granular formulations options will basically be AgLogic 15G or Thimet 20-G,” Greene says. “As far as liquids, you can go with something like imidacloprid or acephate.

“Additionally, we just published a paper on the effects of planting date on crop injury from thrips. Insecticide treatments are especially critical early-season with a slow-growing crop to minimize yield loss and to ensure the crop isn’t delayed.

“And some of the preventive materials are essential basically throughout the whole planting window, but later in the planting window a seed treatment or an in-furrow application might be enough to help you avoid making a foliar spray. Our data show that with low to moderate thrips infestations, if you plant late in the planting window — late May, maybe early June — you can almost use nothing for thrips.”

(Effects of planting date on thrips (Thysanoptera: Thripidae) in cotton by Kerns, C. D., J. K. Greene, F. P. F. Reay-Jones, W. C. Bridges: https://doi.org/10.1093/jee/toy398).

THRIPS MIGRATING FROM WHEAT

West Texas had a wet fall and planted a lot of wheat that will go to grain, graze, or cover. “Wheat provides an excellent host for thrips, so we anticipate we’ll see heavy thrips infestations at cotton emergence,” says Texas A&M AgriLife Extension IPM Agent Kerry Siders. “This year, if we miss treating at planting, we’ll miss a valuable opportunity to manage thrips, which are our No. 1 early-season insect pest.”

A seed treatment and/or an in-furrow insecticide treatment are essential to thrips control. Cotton growers have several good options for both. “For example, the in-furrow liquid options include Velum Total, which is also a nematacide, and Admire Pro,” Siders says. “Additionally, if we miss the at-planting opportunity or thrips pressure continues after some of the early products play out, we have several very effective foliar treatments, including acephate, Orthene, Bidrin, dimethoate, and Radiant.

“We get busy planting, and sometimes we ignore the first emerging fields, which are the ones that are the most susceptible to thrips. After emergence, we really need to have someone out there looking at the crop at least every three to four days to make sure the insecticides are controlling thrips.

“If the weather turns cloudy, cool, and rainy and slows cotton growing off, the door opens for thrips problems. Checking the crop regularly is where the independent crop consultant can really help growers keep up on insects, weeds, and disease so they don’t lose the earliness factor.”

LAYING THE FOUNDATION

When considering early-season insect presence, Arizona cotton growers are urged to focus their attention and energies on laying the foundation for a successful weed management season, according to University of Arizona Entomologist and IPM Specialist Peter Ellsworth.

“Early-season is critical to season-long success in weed management, and can pay dividends in insect management, too,” he says. “With the exception of the oddball occurrences — darkling beetles marching out of the desert into new stands of cotton, unusually severe pale-striped flea beetle pressure prior to true leaf development, or mass migrations of false chinch bug nymphs from rapidly drying-down or killed weeds — growers should accept the arrival of insects into their early-season cotton fields with a welcome mat.

Why? Because many that are arriving are actually quite beneficial to the health of their fields, and the efficiency of pest control provided by predators and other natural enemies pays dividends all season long. “The plant-feeding insects, which are also arriving in early-season cotton fields are, in fact, the fodder needed to feed and sustain the many predators that inhabit our fields,” Ellsworth says.

“While growers think about whiteflies mostly when they need to control them mid- to late-season, they are in fact colonizing cotton seedlings as soon as cotyledon leaves emerge from the soil. That’s actually a good thing because many predators depend on whiteflies as food in order to multiply in our early-season fields.

“Predators like big-eyed bugs, minute pirate bugs, and Collops beetles all rely on the easy meal that whitefly eggs and nymphs represent. In the case of whitefly control, there are even thresholds for these predators, which can allow pest managers to make more informed decisions, potentially delaying the use of insecticides (see https://cals.arizona.edu/crops/cotton/files/wfBIT.pdf and https://cals.arizona.edu/crops/cotton/files/PredatorToPreyRatios.pdf).”

As well, growers might worry about thrips and the potential damage they can do to emerging cotton. “However, this is one time when ‘curb appeal’ or the look of the cotton should not govern a grower’s actions,” Ellsworth says.

“That’s because the main species of thrips in cotton, the western flower thrips, is in fact a key predator in our system, and central to the prevention of mites from breaking out, and very important in whitefly biological control, too. Yes, thrips can molest the cotton plant, feeding on both plant and insects. But by and large, growing conditions in Arizona are so favorable that control measures against thrips should not be necessary.”

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