The widening specter of glyphosate-resistant pigweed throughout the Southeast will force producers to get more creative in terms of crop decisions, says one scientist.
For now, one thing is certain. Resistant pigweed is spreading rapidly through different parts of Alabama.
"It's just a matter of time perhaps before every field in south Alabama will have resistant pigweed," says Dr. Michael Patterson, an Alabama Cooperative Extension System weed scientist and Auburn University professor of agronomy and soils.
"We're not going to stop it, which means it's going to have to be managed using herbicides with different modes of action and crop rotation."
For many of them, a potentially attractive option remains corn production. Why? Partly because it can be grown using atrazine, which remains an effective weapon against pigweed.
Patterson credits one grower, Eufaula producer Walt Corcoran, with making optimal use of corn rotation.
"Using atrazine [which is permitted with corn but not the other principal row crops], he was able to keep the fields relatively free of pigweed," he says, adding this provided Corcoran with a distinct advantage when he returned to cotton again this year.
But Patterson praises Corcoran for adopting another practice that will prove essential in controlling pigweed.
"He ensures after corn harvest that these fields remained burned down to prevent pigweed from making seed. This is very important because after mid-August harvest pigweed can still make seed until frost if left uncontrolled."
Patterson says this precaution should be viewed as an essential control measure for any Southeast Alabama producer who adopts corn rotation — a practice that also provided an extra advantage when he returned to cotton this year.
On the other hand, farmers who are just now dealing with resistant pigweed and have not adopted this essential practice have not fared so well. Some may even face calamity.
"By the time they realize that the Roundup (glyphosate) isn't doing the job, the pigweed is too big to deal with effectively because, with cotton, we simply don't have any other tools in the toolbox to cope with the problem.
"At that stage of the game, when you've got cotton a foot tall and pigweed 18 to 24 inches tall, you have only two options — hand weeding, which is a losing proposition, or mowing down the crop.
"Frankly speaking, with cotton right now, those are the only options," Patterson says.
With cotton, the weeds between rows have not been the biggest challenge — the ones within the rows have.
While the weeds between the rows can be dealt with using hooded sprayers and directed sprays, weeds within the rows are virtually impossible to control.
This growing season, as the reality of glyphosate resistance is brought home to many of these producers, 2010 will likely be remembered as a critical year in the struggle against this growing menace.
"A lot of growers are beginning to realize that they have this resistant weed and that they can't kill it with Roundup," Patterson says. "So, if they are growing cotton and they don't change their production practices this year, namely using residual herbicides from the very beginning, they may lose their crop.
"That's what growers in Georgia discovered three years ago."
The bottom line: Cotton producers in areas of Alabama beset with pigweed have to adopt more intensive production practices with heavy emphasis on residual herbicides.
"If you don't follow that program in these areas, it's almost going to be impossible to produce a cotton crop," Patterson says.
"You may harvest some cotton, but it won't be much and the quality will be low. It's almost a guaranteed ticket to the poorhouse."
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