Cotton insect pressure changes yearly

One thing you can depend on in cotton insect control — no two years are ever alike, says Ron Smith Auburn University Extension entomologist. “This year, like most years, is a little bit different from the last,” said Smith at the recent Alabama Cotton Field Day Celebration held in Prattville.

An emerging insect pest that is proving to be a major problem in central Alabama and is spreading to other parts of the state is the grasshopper, said Smith in presenting a status report on Alabama's cotton insect situation.

“And it's not just a problem in Alabama,” he says. “It's also in the Florida Panhandle and in Georgia. Each year, we're spraying more acres for grasshoppers. They're particularly attracted to the young stems of the seedling plant just after it emerges. They'll even catch it in the crook stage if they can get to it.”

The grasshopper problem appears to be over after the stem of the cotton plant becomes tough, adds Smith. “Grasshoppers are relatively easy to control in April, when they're immature. About a month later, they're very difficult to control with the same chemistry. We need to go with much higher rates at that time.

“We also saw this year that one spray may not be enough for grasshoppers because there's a reservoir out there in the wild host weeds, and they can move back into that area,” he says.

Alabama cotton producers in some areas also have treated for crickets and other “odd-ball” insect pests this year, says Smith.

Although some growers have reported heavy thrips pressure in 2002, Smith says it's closer to an average year across the state. “I can't remember a year when it hasn't been heavy for thrips. I'd say it's an average to heavy year, which means we've seen plenty of pressure. And, there's no perfect treatment for thrips.”

Alabama growers from one end of the state to the other have had problems this year with the three-cornered alfalfa hopper, notes the entomologist.

“We saw some of the pest two years ago in central Alabama. But it was widespread this year, from the Gulf of Mexico to the Tennessee state line.

We noticed them for the first time after a weather front had passed through, and a lot of true leaves were lying on the ground. The three-cornered alfalfa hopper had moved up and cut off the true leaf, and then the wind came through and blew them off.”

Alabama cotton producers have the potential to have more tobacco budworms this year than they've had in several years, says Smith.

“Beginning as early as April or May, reports started coming out of Georgia that they had more budworms on tobacco than they had seen in some time. In early June, we began putting out pheromone traps in the Wiregrass region of southeast Alabama, and we were catching up to 100 moths per night. That's more than we've captured in several years.

“Later, we saw a number of fields with 10 worms and 20 to 30 eggs. Most growers have let that generation go, and that was the right thing to do. At the time, there just wasn't a lot of fruit at risk. But with the next generation, we could see more tobacco budworms than we've seen in a long time.”

This generation could be seen in July in the southern part of the state, says Smith. Then, a week or two later, it'll move north.

“I believe we'll see another moth flight, and it'll be about 100-percent budworms again. If the flight lasts about 10 days, we may begin to see bollworms moving from corn. We may go from a budworm population in early July to a bollworm population in the middle of the month.”

With the proper treatments, growers can take advantage of that situation, says Smith. “If we have numbers big enough so that we need to spray, that first application in July should target budworms. These treatments should be made with the new chemistry, such as Tracer or Steward. Ten days later, we can treat for bollworms with a pyrethroid and do an excellent job.

“If you spray pyrethroids on budworms, you'll strike out. And, if you come back with Tracer or Steward on the bollworms, it'll be less effective than if you had used pyrethroids, and it'll cost much more. Be sure you match up your worm chemistry with the species in the field.”

A movement of tarnished plant bugs were being seen in north Alabama in late June, but no movements were detected in the central part of the state, says Smith.

“Weather during May was a factor with tarnished plant bugs. We were dry in most parts of the state and they failed to grow in large numbers on wild hosts. They received more rainfall in the Tennessee Valley, so they had millions more plant bugs on the wild hosts.”

Stink bugs potentially could be a serious problem for growers in central to south Alabama, says Smith. “They were coming out of harvested wheat by the bushel. We're talking primarily about Southern green stink bugs with some brown stink bugs mixed in with them.

“They've been heavy in pre-bloom cotton, and some cotton has been sprayed because they were damaging the terminals. The big question is what are stink bugs doing before we have bolls? I don't believe at this time that stink bugs are damaging squares. They're looking for protein from the seed.

They really aren't a serious threat until we have small bolls.”

Cotton that has been blooming for several weeks soon will have thumb-sized bolls, says Smith. “Stink bugs have been out in the field for a while, and they're hungry. They prefer a boll that's about the size of a quarter in diameter. But I'd predict that stink bugs probably will start going for thumb-sized bolls this year, and they will be out there in tremendous numbers. And don't think stink bugs will cycle out. Their life cycle is 30 to 60 days, so you have to kill them.”

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