For Tillar, Ark., producer Steve Stevens, weed control across his 4,500 acres has gone from simple to complex. But residual herbicides, rotation and two weed technologies are helping him manage it. He’s also using a new nozzle that can help deal with the risk of drift in a two-herbicide technology system.
Stevens, who farms corn, cotton and soybeans, uses both LibertyLink and Roundup Ready technologies to combat weed resistance. But it’s taken a few years for him to understand how they could work together.
“When I was first presented with the Liberty option in 2004, I wanted another system that was like the Roundup Ready system. I soon learned there would never be a system as good or as inexpensive. So what I’ve learned is that I need to use the Liberty system to preserve the Roundup Ready system.”
Even though they aren’t in every field, resistant weeds are a part of every decision Stevens makes. There’s a lot at stake. “If you let your guard down and let your farm become wrapped up in resistant pigweed, your land values are going to go down on that farm because it’s going to take money to get it back.
“We’re going to have to be good stewards of the Liberty system by using lots of residual herbicides so we don’t let resistance get Liberty. Liberty is our last defense.”
Stevens’ resistance management plan is to rotate 30 percent to 40 percent of his crop acres to LibertyLink “to keep weeds mixed up. I don’t want those resistant weeds on my farm.”
Stevens plants Pioneer/Herculex corn hybrids, which come with the option of the dual herbicide technologies of Roundup Ready and LibertyLink, and also plants non-Bt corn that is Roundup Ready only.
“Corn will give you more options on weed control,” Stevens said, “but I don’t let a field grow up thinking I can clean it up with corn. I think that gives you a false sense of security.”
Cotton acres are planted in a combination of Roundup Ready and LibertyLink varieties. “We’ve been planting LibertyLink cotton since 2004. We spent three years learning how to use the technology, and waiting on varieties that had good yield potential. We have those now.”
LibertyLink cotton goes on fields with a history of resistant weeds because residuals applied on those fields may not always receive an activating rainfall. “LibertyLink gives you an out.”
One of Stevens’ cotton varieties is FM 1944GLB2, which has both Liberty and glyphosate resistance.
Stevens’ soybean varieties are either Roundup Ready or LibertyLink technologies.
As for LibertyLink soybean varieties, “I’ve done very well with the Halo 4:94. We cut 70 bushels on that variety. I also like the Halo 4:65. On good strong ground, the Halo 5:25 has done well. Halo 5:65 has a good salt package in a Group V.”
Stevens bought an additional sprayer to help insure that he can get over ground quickly if he has too. “We use a John Deere 4710 as a primary sprayer, but because of the pigweed situation, we added a John Deere 4630. The long and short of it is we’re going to have to purchase more spraying power than we think we can really justify, just so we can be timely.”
Drift is not acceptable with two weed control technologies on the same farm. On the other hand, good coverage of a weed is essential too, notes Stevens. He runs a TurboDrop Asymmetric Dual Fan nozzle, from Greenleaf, to capture both benefits.
“We found it to be an extremely good nozzle for coverage. It was built for higher speeds. We found that in 10 mile an hour winds, we could spray both sides of a weed. It’s just that much better.”
The nozzles create medium droplets at 60 pounds per square inch, which is required for the application of Liberty. It’s also used for other applications, from burndown through defoliation. One feature of the nozzle is that it uses multiple angles of spray orientation into the canopy.
“It gives us a medium droplet with very few fines,” Stevens said. “If we start getting close to a neighbor or a sensitive crop, we slow down to make our droplets larger to decrease drift potential even more.”
Residual herbicides are also important resistance management tools, according to Stevens. “I am buying into what the weed scientists are saying. If the residual lasts 21 days, I try and come back with another residual at 14 days, because I may not get a rain when I need it, or I might get a rain that keeps me from being timely.”
Stevens is also using the “flag the technology” system in which a weed control technology is identified by various flag colors placed in plain view of sprayer drivers. But the system has a few kinks to work out. “If you get into a good thunderstorm, there’s a good possibility the flag will blow off.”
Stevens uses a herbicide map generated from Farm Works software to create color-coded maps indicating how crops and technologies are distributed across his operation. Stevens’ sprayer drivers also use a hand held wind speed and direction meter for recordkeeping purposes.
Glyphosate-resistant pigweed, horseweed and Italian ryegrass have all made appearances on Stevens’ fields, demanding that he stay vigilant. It comes at a cost.
Herbicide costs are about 20 percent higher. Time and labor costs have increased by almost as much.
“It’s just a fact of life,” Stevens said. “We’re going to spend more money to stay on top of it. We not only have horseweed and pigweed to worry about, but Italian ryegrass is running a close second. I don’t know what we can do about it. We just have to do what we have to.”
One key is to aim high, notes Stevens. “We’re going to have to keep these residuals going, and we’re going to have to try and get every last weed. We can’t let one go to seed on a ditch or a turn row or in the field. Today, if you see a pigweed, you have to believe that it’s resistant.”