What is in this article?:
• One of the hindrances to resistance management is economics.
• Acreage has expanded and people don’t cultivate anymore, so to go backwards is a hard pill to swallow.
• There’s also denial about having or ever getting the problem.
Key to survival?
Many say that residual herbicides are the key to survival, and that every acre that is planted should have a residual on it, he says. “As a weed science community, we should never promote the absence of residuals. And in a lot of cases, one is not enough. You might use two or in cotton you might need three to do the job.”
More emphasis should be placed on removing escaped plants so they don’t put seed back into the field, says Prostko. Also, in Georgia, there has been a significant increase in the interest and use of non-selective applicators.
“We’re not actively promoting these with cotton and soybeans, but we are with peanuts. We feel we can get the height differential in peanuts to give us the kind of control we need where we can’t consistently with other crops. There’s still a lot of work to be done.”
And of course, hand-weeding is another option, he says.
As for post-harvest treatments, some of this has been done previously in Georgia for tropical spider wort, he says.
“We’ll start harvesting corn at the end of July, early August, and we might not get our first frost until mid-November. If you look at the published data, pigweed can go from seed to seed in 35 days. We have ample time between corn harvest and first frost for another crop of pigweed to become established. So we have to start doing something about that if we’re going to get a handle on it.”
But it depends, he says, upon the size of the weed, and if you’re going to plant a small grain. “I don’t think we can get very effective control if a pigweed is bigger than 6 inches. Gramoxone, 2,4-D and dicamba have been used quite a bit. You can put out a residual in the fall, but I wouldn’t if I planned on planting a small grain in November.”
Georgia growers can finally stop worrying about Palmer amaranth at about the middle of October, he says.
As for the future, Prostko says he’s extremely concerned about developing resistance to the PPO herbicides.
“In Georgia, we’re using a lot of Reflex and Valor, and we’re extremely concerned about keeping the longevity of those products. Some weeds have already developed resistance to this mode of action, including two species of pigweed. It will happen, and it may be out there already and we haven’t seen it. You could conceivably use 16 PPO herbicides in four years — that’s definitely a bad idea.”
He’s also concerned about the abuse of Ignite.
“Abuse is a harsh word, but the weed science community was not harsh enough in the case of Roundup Ready. I want to be extremely harsh and say we’re abusing Ignite.
“In some cases, we’re seeing three applications made on crops, and that’s a recipe for resistance. We already have resistance to Italian ryegrass and goosegrass to Ignite. It will happen. I hope we learned our lesson from what happened with Roundup.”