Cotton defoliation could be a real challenge this year for producers in Alabama's Tennessee Valley, especially considering the variability of the crop.
“Our crop across north Alabama is extremely varied. We've got cotton that is almost completing bloom or cotton that either hasn't started to bloom or is just beginning to bloom,” said Charlie Burmester, Auburn University Extension cotton specialist.
Burmester gave an update on this year's crop at the recent Alabama Cotton Field Day, held at the Tennessee Valley Research and Extension Center in Belle Mina.
“Generally speaking, we can mature a boll or bloom by about Aug. 21 to Aug. 25, and that gives us a full three weeks. If we have a really good fall, we might can push that to four weeks. But we're getting close to running out of time,” he says.
Most of the cotton in the region is one to two weeks behind due to excessive rainfall during the season, says Burmester. “You can find cotton here that's a week behind, but it's loaded with bolls. Then, you can go down the road and find a completely different story. Where the ground is low, and the cotton was drowned out, the crop is delayed.
“Depending on weather conditions, defoliation is going to be a challenge because we'll have several different stages of cotton in the field at the same time.”
This may be a year, says the agronomist, when using a plant growth regulator is very helpful. “In looking at this later cotton, the squares you have now probably will be the only squares that you'll be able to mature. At this point, you shouldn't be worried about the squares that are put on later. Pix it, and try and get it to set squares and make bolls. Then, shut it down, because those later squares are just insect food.
“As long as you have enough plant now to harvest, I wouldn't be afraid to put 8 ounces of Pix on it and try to slow it down. One thing we've seen with Pix over the years is that if it controls growth, and we can get about five days of maturity out of it, we can get in five days earlier. And in a year like this one, five days could mean a lot,” he says.
Reviewing insect pressure
Cotton producers in the Tennessee Valley have had an “average” thrips year, says Barry Freeman, Extension entomologist. “Farmers had a tough time with cotton in the seedling stage, but it was more weather related than thrips problems. Thrips have a couple of stages in the soil surface, and the rainfall this past spring just wasn't good for them,” says Freeman.
North Alabama growers had a few aphid problems in late May and again in late June, but it wasn't out of the ordinary, he says. “We anticipated a bad plant bug year. The way it played out, plant bugs started to move to cotton in mid- to late-June, like always. It wasn't a heavy migration, but they never let up until the end of July,” he says.
Plant bugs haven't ravaged cotton, he adds, but they've been a steady pest for a long time. “Farmers who haven't been in their fields controlling plant bugs probably have some now that could stand cleaning up.”
For the third or fourth consecutive year, growers also have had serious problems with the two-spotted spider mite, he says, and control has been difficult.
“This is a pest that does need controlling because it will defoliate cotton,” notes Freeman. “New growth has been covering up some of the mite damage. As the plant quits growing vegetatively, that damage starts to show. We don't need to let that pest go too far. It's expensive to control, and it requires specific products.”
The entomologist says he is also concerned this year about corn earworms. “Starting in late July, we began flushing a lot of moths. Usually, if I scout a field of cotton and flush four or five moths, they get my attention. We're flushing large numbers and the egg counts are increasing. We're also starting to find a few caterpillars.”
Bt cotton should provide 60 to 65 percent control of the corn earworm, says Freeman. “Some can break through, but pyrethroids still control that pest.”
In central Alabama, at the Prattville experiment field, corn earworms have been laying eggs since July 17, says Ron Smith, Extension entomologist.
“They've spread over the entire farm — we're talking about numbers we haven't seen since 1995. We're seeing egg lays of an egg or more per plant. Some plants in untreated conventional cotton had five worms,” says Smith.
It's important, he adds, that growers pay attention to the number of corn earworm or bollworm moths. “They shouldn't be difficult to kill, and pyrethroids do a good job,” he says.
Stinkbugs also continue to be a concern for Alabama cotton producers, says Smith. A higher percent of the stinkbug population throughout the growing season has been the brown stinkbug, he says.
“The brown stinkbug may be more winter-hardy than the green stinkbug,” says Smith. “But the green stinkbug also is coming into the system, so we have a mixture of both species.”
A distinction is made between the brown and green stinkbug, he says, because chemical controls are not the same for both pests. “In general, pyrethroids do a good job on the green stinkbug. Other than Capture, they don't do a good job on the brown stinkbug.”
Consultants in southwest Georgia have reported that the new pyrethroid Mustang Max has worked well on brown stinkbugs, says Smith. “Our work shows that Mustang Max falls in line with other pyrethroids, with about 35 to 40 percent control. Capture will give you about 60 percent, and phosphates like Bidrin will take you up to about 100 percent.”
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