Bindweed's pretty flowers never fool farmers. They know the pesky perennial can strangle a crop.
But postemergence applications of Roundup Ultra (glyphosate) herbicide may be the management tool soybean growers need to control the menacing weed and get a jump on its root development for the next year's crop.
Clay Salisbury, Texas Ag Experiment Station research agronomist, reports solid bindweed control with over-the-top herbicide applications on Roundup Ready soybeans. At his Texas Panhandle research fields near Etter, treated fields were clean last year, while untreated fields were bound by bindweed.
"This is not a magic bullet for bindweed because there isn't one," points out Salisbury. "But with the glyphosate-ready soybean varieties and postemergence herbicide applications, growers can manage the weeds and be one year closer to reducing bindweed populations."
Of course, the program won't work for varieties without the Roundup Ready gene. But soybeans with the gene can be treated with 24 to 48 oz of Roundup Ultra per acre from emergence through flowering. For broadleaves, like bindweed, the initial application should be made when they are 4-8" tall.
"This should provide good in-season bindweed control," says Salisbury. "But since it is a perennial weed, an application should also be considered for the fall."
If there is regrowth, a second application of 32 oz is recommended. "This will help provide residual benefits toward controlling bindweed in soybeans, cotton or corn the next year," says Salisbury.
He points out that fall applications are more effective in slowing down bindweed roots.
"There is usually better efficacy with fall applications, because summer applications are not as effective in translocating (the herbicide) to the roots."
Fall applications can also be good harvest aides.
"If bindweed runners reach six to 12 inches, they can really slow down a combine," says Salisbury. "So that would be a good point for a late-year application."
He adds that, even if a soybean crop is short due to low rainfall in semiarid areas, growers will still earn enough from the crop "to pay for good bindweed control that will benefit them the following year."
Another product to be considered for over-the-top bindweed control is Touchdown 5 (sulfosate) from Zeneca, says Salisbury. Check with your chemical supplier to make sure it's labeled for use in your area.