There’s no doubt about it. Wherever weeds are during the season, they cause problems.
- Early season weeds steal nutrients during a critical growth phase that young cotton plants need to produce healthy bolls.
- Left until late season, weeds will affect harvestability and fiber quality.
Both types of weeds are a problem, but early season weed pressure may be the most detrimental to your bottom line because early season cotton needs every advantage it can get to make a successful start.
During the first eight to 10 weeks the crop is in the ground, make it a habit to check your fields every couple of days. Problem weeds, like pigweed, can grow 1 to 2 inches per day under the right environmental conditions. With such vigorous growth, you can quickly find yourself in a tough situation.
There are a few best management practice guidelines from the Herbicide Resistance Action Committee that can help.
- Apply integrated weed management practices and use multiple herbicide modes of action in the field.
- Start with a clean field and control weeds early by using a burndown treatment or tillage in combination with a pre-emergence residual herbicide as appropriate.
- Use the full-recommended herbicide rate and proper application timing.
- Scout fields after herbicide application to ensure control has been achieved. Avoid allowing weeds to reproduce by seed.
- Use cultural practices such as cultivation and crop rotation, where appropriate.
Growers in both the east and the west of the Cotton Belt tell the same story when it comes to early-season weeds: Scout and eliminate weeds early in the season, so they can’t take over your crop. The use of FiberMax® and Stoneville® varieties with the LibertyLink® trait is also important for success. Let’s look at two growers’ experiences to learn more.
West Texas grower David Pearson had a tough wake-up call to resistant weeds on his farm in 2013. “That July we had to plow the cotton up,” he said. “It was tough to do, because it was one of the best stands of cotton I’ve had, but I didn’t have the LibertyLink trait and I wasn’t able to manage the pigweed when it got out of control.”
In 2014, Pearson planted FiberMax and Stoneville cotton and used Liberty® herbicide on ST 4946GLB2. “I had never used Liberty, and I’d heard lots of stories about how to use it, how to spray it and how to be effective with it. You’ve got to wait and time it right, but if you do what’s right it works. We did both of those things in 2014 and were extremely effective with killing the glyphosate-resistant pigweeds. To be able to grow cotton out here in West Texas with the resistant pigweed, we’ve got to have Liberty,” he said.
In Georgia, Lamar Black has had glyphosate-resistant Palmer amaranth on his farm for many years so he keeps a close eye on his fields to manage weeds quickly.
“I depend on Liberty herbicide to control Palmer amaranth,” he said. “I planted ST 6448GLB2, and it worked very well for me. In my area with Liberty, you need to wait until later in the morning before you start – the hotter it is and the brighter the sunshine, the better the Liberty works. And when I’m spraying Liberty on cotton, I usually use 20 gallons of water per acre — that’s my standard rate.”
Growers like Pearson and Black understand the importance of a system that works on a broad spectrum of weeds, including those that are tough-to-control and their results showed it in 2014. To get the most from Liberty herbicide, remember this acronym: S.T.O.P.
Start early with the first application.
- Early action against weeds is key, so start early with the first application soon after emergence. Scouting weeds and taking early action influences your success.
Target less than 3-inch weeds.
- Successful control starts when weeds are small and easiest to manage.
- Liberty is a contact herbicide, requiring thorough spray coverage, so how Liberty is applied is key to Liberty’s effectiveness and your ability to control weeds. Warm temperatures, higher humidity and bright sunlight are ideal application conditions.
- It starts with the right nozzle. Pick one that generates a medium spray droplet.
- Use plenty of water — at least 15 gallons per acre to ensure full coverage. In arid conditions or where a dense canopy exists, use 20 gallons per acre.
- Watch ground speed. Keep ground speed less than 10 mph for full coverage.
Pair with residuals
- The key to preventing resistance is to reduce the pressure caused by using a single herbicide mode of action. Make sure to use multiple effective modes of action. Use pre-emerge residual herbicides and a residual tank mix partner for best results.