This week’s likely to see a lot of corn and soybean harvest progress around the nation’s midsection.
So, if your harvest pace catches up and you end up with a little more time than the last couple of falls to get some fieldwork done, fall herbicide treatments may be on your to-do list. If you’re going to spray this fall, don’t forget a few key tips to get the most out of your time, money and effort, one expert says.
Keep these 5 points in mind when you go to put down herbicide in the fall, says Ohio State University Extension weed scientist Mark Loux.
- First, application timing: When is best? As long as you beat a “hard freeze,” you should have fairly good control. But, once temperatures are regularly dipping well below 32 degrees, your window’s likely closed.
“Anytime between now and Thanksgiving will work, and possibly later. We have applied into late December and still eventually controlled the weeds present at time of application,” Loux says. “Once hard freezes start to occur, there is usually a substantial change in the condition of certain weeds, such as dandelion and thistle, that renders them less sensitive to herbicides. We discourage applications during periods of very cold weather which can occur starting about Thanksgiving, and also (obviously) when the ground is snow-covered.”
- Now, what about crop residue left in the field? That’s a concern in a growing number of fields where conservation tillage and no-till are common practices. But will all that “trash” keep your herbicide from working? Not necessarily, Loux says. But, it never hurts to play it safe if you’re worried about overall spray efficacy.
“We have not worried about this, and the herbicides seem to work regardless. Most dealers I have asked seem to have the same impression,” he says. “On the other hand, it probably wouldn’t hurt to wait a while after harvest to let the residue settle down, and the weeds to poke through. Dense crop residue usually prevents marestail from emerging anyway.”
- Next, keep it simple. The goal of fall-applied herbicides is a simple one — to knock down weeds that are already emerged — so don’t make things more complex than they need to be, Loux advises.
“Keep in mind that the primary goal is control of weeds that have already emerged. This is hard to accomplish with a single herbicide, but there are a number of relatively low cost two-way mixtures that easily achieve this goal. Our philosophy has generally been to start with 2,4-D, and then add another herbicide that results in more comprehensive control. Herbicides that make the most sense to add to 2,4-D based on our research: glyphosate, dicamba, metribuzin, simazine, Basis (and generic equivalents), Express (and generic equivalents), Canopy/Cloak DF or EX, or Autumn Super,” he says. “These allow either corn or soybeans to be planted the following year with these exceptions: simazine — corn next year; Canopy/Cloak — soybeans next year; Basis – possibly restricted to corn based on rate and geography. We do not see the need for three-way mixtures, although a case can be made to add a low rate of glyphosate to a two-way mix to control grass or improve activity on perennials.”
- What about including a residual herbicide? Don’t bother this time of year, Loux says. Especially if your applications have to wait until later in the fall, they’ll likely degrade, dilute or get flushed away, leaving “inadequate concentrations of herbicide remaining in spring to control emerging weeds.
“Almost all of them peter out over the winter and fail to provide any control of spring-emerging weeds. Our research has repeatedly shown that applying other residual herbicides in the fall to get control in spring is a waste of money,” he says. “The good news here is that any effective fall herbicide treatment with or without residual will result in a weed-free seedbed in spring, usually into April, so that the spring-applied burndown/residual treatment just has to control small weeds that emerge in the few weeks prior to planting. That is the goal.”
- Finally, go easy on the amount of herbicide you put down this time of year, both to keep your total weed control budget in check as well as create the most effective weed-kill, Loux says.
“It doesn’t take a lot of herbicide to control weeds in fall, just the right ones. There is a tendency for some manufacturers to promote an expensive mixture of too many herbicides that just isn’t necessary. Avoid most residual herbicides, and also those that mainly ‘speed up the kill,'” he adds. “Consider that fall treatments should comprise not more than about 25% of your total herbicide budget for a crop, and it can be accomplished for even less than that.”
(Source – http://www.agriculture.com/news/crops/5-tips-f-successful-fall-herbicide_2-ar45729)