Plant Bugs Are Enemy No. 1

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According to data from Mississippi State University, tarnished plant bugs are not only the No. 1 most damaging pest, they are by a wide margin. The study sponsored by the Cotton Foundation shows that across the Mid-South, plant bugs reduced yields by 115,451 bales in 2007, nearly double that of the next closest pest – the tobacco budworm/cotton bollworm complex.

A Peaceful Coexistence

Preventing corn insects from becoming cotton’s problem.

As corn begins to mature and dry down, insects will be moving to the greener pastures of nearby cotton fields.
Roger Carter with Agricultural Management Services in Clayton, LA, advises his cotton growers to take several steps that will hopefully minimize the impact of plant bugs moving out of maturing corn and into green cotton. His recommendations begin with keeping corn fields as far away from cotton as possible. “If planted side-by-side, leave a strip of non-planted cropland – 32 to 26 rows wide – between the corn and the cotton,” says Carter. “This reduces the ‘breeding ground’ that develops immediately adjacent to corn.”
If corn and cotton are planted side-by-side, he says to begin treating the first 100 rows of cotton immediately adjacent to the corn with a plant bug adulticide plus Diamond insecticide, at 6-9 ounces per acre, as soon as plant bug movement is detected.
“And, if possible, sidedress with 5 pounds per acre of Temik once cotton reaches the sixth to seventh node,” says Carter. “Growers also should maintain a regular spray schedule with a five-day interval until plant bug movement stops and bugs are manageable.”
In Alabama, most growers are aware that corn is a great reservoir for stink bugs, says Dr. Ron Smith, an Auburn University Extension entomologist. “As corn dries down, stink bugs will move in a relatively short time to another source of food. At that time, cotton is at the perfect stage, as we’re just beginning to set bolls. If cotton is nearby, stink bugs will logically move into it,” he says.
It’s well known that stink bugs can damage cotton bolls, and they prefer that bolls be about half grown, says Smith. “But if stink bugs get into cotton earlier, they will feed on younger bolls,” he explains.
Although it didn’t happen in Alabama this past year – possibly due to high temperatures and extreme drought conditions – bollworms can move in great numbers into cotton. “You’re raising, in most years, thousands and thousands of corn earworms per acre in a corn crop, and they’re going to move into cotton in the next generation. …That would be the late July or early August generation in cotton,” says Smith.
This would be a perfect time, he adds, for overspraying pyrethroids. In most areas and in most years, pyrethroids still are the most economical control of corn earworms. They also would provide excellent control of the Southern green stink bug, he says. Later on in the season, Smith advises growers to use a product like Bidrin to control stink bugs. “This past year, we didn’t see that many stink bugs – they crashed in the spring and then did not build up in corn and spill over into cotton. They eventually were in cotton, but it was later in the season,” he says.

Editor’s note: Information for this story was provided by Doreen Muzzi, an agricultural journalist from Shaw, MS, and a regular contributor to Cotton Grower.

In the Delta area of Mississippi, growers spent a staggering $67.50 per acre to combat plant bugs, the study says. Louisiana and Arkansas spent roughly half that. A majority of the blame was placed on plant bugs that migrated in waves out of maturing corn and into still-green cotton. Hypothetically, plant bug control could have approached 100% on Monday, and a grower could be spraying a new infestation only a few days later.

This year, an additional host crop and another pest could double the trouble. According to USDA estimates, winter wheat acreage across the Mid-South has nearly tripled since 2006 to 1.67 million acres this season. Wheat is a very good host for thrips, and when wheat begins to dry down, they could beat tarnished plant bugs to adjacent cotton fields.

“There’s not a lot of things you can do preemptively, but you need to be aware of it,” says Mississippi Extension entomologist Dr. Angus Catchot. “When cotton is in an area where there is a lot of wheat, generally we can expect thrips. It’s hard to predict what any insect is going to do, but generally we are going to have high thrips numbers with the amount of wheat we have in the state in fields that are adjacent or close to cotton.”

Catchot says essentially 100% of Mississippi’s cotton has either an on-seed treatment or Temik on it. “That does work well,” he says. “We had an increase in wheat acres last year and we had significant thrips damage. People wondered at that time if seed treatments were holding up, and they were – it was just extremely high pressure.”

The proof of that, Catchot says, was in test plots scattered through the state. “We did have a little damage on plots with seed treatments,” he explains. “But we had plots next to those that were not treated with anything for thrips and the plants were almost dead.”

Cut Out Cutworms

The higher wheat acreage also is causing producers to modify their preplant burndown herbicide applications on cotton land because of the potential for drift onto neighboring wheat fields. “Cotton growers and pesticide applicators are concerned about the non-target effects of the burndown treatments and have tried to wait for days when wind is not a factor. By trying to be good stewards, they ended up spraying later than normal,” says Dr. Roger Leonard, an LSU AgCenter entomologist. “Producers tried to control heavy vegetation, which is dying slowly, and some will likely be present when planting occurs. If the soils are cool, cotton is going to emerge slowly, and the opportunity for cutworm problems could be quite extreme where there is residue.”

In those cases, Leonard says pyrethroids should be applied as a preventive application. “This treatment can be applied just prior to planting, at-planting, or immediately after planting. It does not matter as long as they put one out,” he adds.

Another consideration is that if a cutworm kills a transgenic cotton plant before the plant-protection trait can be expressed, you’ve lost more than just that plant. “You are not going to recoup that investment if a cutworm takes that plant out – you’ve lost the technology up front,” Leonard explains. “Don’t forget about cutworms.”

Caption for Sidebar:
Cotton next to corn was a common sight in 2007.

Chart:
Mid-South Insect Losses in 2007 (in bales)
Source: Mississippi State University and Cotton Foundation

Gantz is the editor of Cotton Grower magazine. Over the years, he has won many National Agricultural Marketing Association awards, including two national NAMAs – one in advertising and one in public relations. Gantz brings hands-on experience, having worked as Sales Manager for an agricultural supply distributor in the Mississippi Delta.

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