To defeat your enemy, you have to understand what makes your enemy tick. Great generals have understood that down through time. If you're fighting your own personal war against marestail, especially in soybeans, and feel like you're losing the battle, step back and make sure you understand the weed, including when it's most vulnerable to control.
Marestail is technically a winter annual, but it doesn't always act exactly like a winter annual. Even so, Bryan Young, a Purdue University Extension weed control specialist, says fall is a good time to begin spraying the herbicide.
"It germinates in the fall and has a rosette," he says. "Ideally, you want to control it in the rosette stage. If it makes it to spring and it bolts out of the rosette and gets very tall, you will have trouble controlling it."
The difference between marestail and most other winter annuals is that the vast majority of winter annuals produce seed by early June or earlier. Marestail can produce seed into August. That's what makes it important, yet more difficult, to control, Young notes.
Liberty is one option to consider if marestail is a problem on your farm. Some companies have recently added several new Liberty-tolerant varieties to their seed line-ups.
"The biggest thing you need to do if you switch to Liberty herbicide is spray it correctly," Young explains. According to Young, that means adding more volume of liquid per acre, and spraying with adequate pressure.
"It's a contact herbicide and glyphosate is a systematic herbicide," he offers. "With contact herbicides, you need to get as much coverage as you can. It typically takes more carrier volume to spray Liberty effectively than to spray glyphosate."
In fact one expert quipped once that the most effective additive to put in the tank with Liberty is more water. Make sure you have adequate volume to get good coverage.