All across Indiana it is getting very green as spring conditions are finally here, but that also means weeds are poking through, including pesky weeds in farm fields. Purdue Extension weed specialist Travis Legleiter says start scouting fields for winter annual weeds.
“As the weather continues to warm the winter annuals are going to continue to grow even though we’re not quite to planting yet,” he said. “Those fields that did not receive a fall burndown, that’s where they are more than likely growing the most in those no-till acres.”
Most fields will require some form of spring herbicide treatment, but the earliest attention should go to those fields that didn’t receive one last fall. Legleiter (right, with Bill Johnson) says you’ll need to take into account both weather and weed size when making decisions about spring burndown herbicide applications.
“You want to get to the weeds the smaller the better, but we also need to consider what the weather’s been. We need to hit the weeds when they’re actively growing especially with these burndowns when we’re using a trans-located herbicide like glyphosate which is most common. We need to make sure weeds are actively growing and the rule of thumb we use for that is several nights above 45 degrees plus a forecast of several more nights of those temperatures. That can assure us that those weeds are actively growing and that will allow the herbicide to work.”
For longer-term weed control a pre-emergence residual herbicide is a good idea.
“Rather than just going out and killing what’s there, looking out to the rest of the summer, and this for guys that are especially dealing with marestail, we encourage those guys to also use residual herbicides. What we need to do is not only make the burndown but also think about what residuals they’re going to include in that burndown. The closer we get to planting the more likely we need to get a residual in there and that will help keep the weeds from coming up after the crops get planted.”
Legleiter added if you’re planning on using residuals, maximize the residual control into the cropping season by applying the products pre-emerge rather than tank mixing it with early spring burndown.
More information about spring burndown applications can be found in the following free, online articles:
* Spring Burndown Applications to Weeds and Cover Crops by Legleiter and Purdue Extension weed scientist Bill Johnson.
* Control of Marestail in No-Till Soybean by Johnson and Ohio State University Extension weed scientist Mark Loux.
Weeds in winter wheat fields also might need some attention as wheat continues to green up. Some fields have winter annual weeds that will require a spring herbicide application in part because of how wheat fared in the bitterly cold winter months.
“In typical years, winter annual pressure in wheat is less of a concern, but with potentially weakened wheat stands, the pressure from winter annuals will be more of a concern,” Legleiter said.
Some of the most important considerations for wheat growers developing a weed-control plan include the wheat growth stage and soybean plant back restrictions for fields that will be double-cropped.
One option, Legleiter said, is to combine spring herbicide applications with topdressed nitrogen. Growers who go this route need to be sure to read herbicide labels.
“Many of the herbicide labels do allow for liquid nitrogen to be used as a carrier but might have differing adjuvant requirements and growth stage restrictions as compared to applying with a water carrier,” he said.
Legleiter also said the use of liquid nitrogen as a herbicide carrier also can mean increased risk of crop injury.
More information about spring herbicides and wheat can be found in a free, online article titled Spring Herbicide Applications on Winter Wheat. The article, written by Legleiter and Johnson, covers a number of herbicides, application timing, plant back restrictions and more.
Source: Purdue Ag Communications