What is in this article?:
• It’s important to overlap pre-emergence treatments and chemistries by following a calendar rather than by driving out into the field to see if pigweeds are emerging.
• When you come out to plant, you’ll think you have a clean field. But you won’t — the pigweeds are there.
Growers shouldn’t be scared of resistant pigweed, they should just go after it.
Turned off dry
Tunhage says he didn’t receive any significant rainfall after May 31 last year. “We might have received 1 3/10 inch until November — we were burnt up. If you take away the competition, and you’re spraying grass herbicides, the only thing that’ll survive is the resistant pigweed.
“If you’re doing a burndown, you may be using a 2,4-D and Dicamba combination, something with a long residual to get you to planting. When you come out to plant, you’ll think you have a clean field. But you won’t — the pigweeds are there. Spray that clean ground with Gramoxone, and put out another pre-emergence. If you have the capability, put out your herbicides before you disturb the ground. Put out herbicides in front of the planter and put out your pre-emergence behind the planter – it makes a huge difference.”
Tim Roberts, a consultant in west Tennessee and Missouri, says that when a cotton crop is emerged, if you don’t have WideStrike or LibertyLink, then there is no rescue treatment for Palmer amaranth resistant pigweed. “If you hood the middles with Gramoxone, you can try post-directed MSMA and Caparol on the row. We often have dry weather during planting time, but we’re getting pre-emergence out 2 weeks to 30 days ahead of planting, depending on if it’s Reflex or Valor, in the hopes of getting an activating rain prior to planting the crop. The pigweed in our area generally starts to come up at about the middle of April — about the time we plant cotton — and we’ll plant until the end of May.
“If you plant on May 10 and put out your pre-emergence, and then you have no activating rain, and you have an emergence of pigweed, you’re hurt. The way to counter that is to incorporate a yellow herbicide — which works pretty well — or apply an early pre-emergence, always with a burndown and something for marestail if that’s a problem. That should make you clean from the get-go. Then we layer our pre-emergence treatments,” says Roberts.
Growers shouldn’t be scared of resistant pigweed, he says, they should just go after it. “In 2009, we had 10 fields my group consulted on. We probably lost 10-percent yield from those fields due to resistant pigweed. We took an aggressive approach in 2010, and cleaned up the crop. We probably got about 95 percent control. We still had pigweeds in the field. Like boll weevils, you can clean them up, and you can manage them and make a crop,” says Roberts.
Resistant pigweeds can be moved by equipment, but they’ll also show up in the middle of a field, he says.
“Be proactive. We figure we’re spending about $37 per acre on resistant pigweeds, but it’s cheaper than attempting a rescue mission. Do your best to keep it from emerging. Your timeframe for getting control is narrow. The information about controlling resistant pigweed starts to sound repetitive after awhile, but keep listening,” says Roberts.