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