Menu

How Temperature and Rain Can Affect Burndown Herbicides

Rainfast Period

Herbicide labels include recommendations on how much time must elapse between herbicide application and subsequent rainfall to ensure good herbicide performance. This is known as the rainfast period.

Generally, herbicide rainfast ratings (Table 1) are based on good growing conditions. Poor conditions may require a longer interval between application and any rainfall to ensure adequate herbicide translocation within the weed before the herbicide is washed off. For many herbicides, any amount of rainfall soon after spraying has the potential to reduce absorption, translocation, and subsequent weed control. If you apply herbicide and it rains before it’s rainfast, herbicide performance will be reduced.

Temperature and Herbicide Performance

Wide temperature fluctuations in the last couple of weeks have led to questions about possible effects on performance of burndown herbicides. The likelihood of decreased weed control due to cool temperatures will vary, depending upon the target weed, herbicide, and rate applied. For example, glyphosate usually performs well under a wide range of temperatures. Best performance usually occurs when the temperature is 60-75°F at application and remains there for a few hours afterward.

When the temperature is lower than 60°F, weed growth slows, resulting in slower herbicide uptake and translocation. This increases the required rainfast period and slows the onset of symptoms and herbicide efficacy. If the temperature is below 40°F, avoid applying glyphosate-based herbicides. If a severe frost is predicted immediately following an intended application, it may be advisable to avoid spraying. If weeds are damaged or under stress before herbicide has properly translocated, control may be reduced.

The ideal solution is to wait for better weather conditions. However, if weed size or other situations dictate that the field be treated now, select a herbicide with excellent efficacy on the target species. Reduced herbicide rate treatments are less likely to provide acceptable control under adverse conditions than when plants are actively growing.

For more information on burndown herbicides, see the 2020 Guide for Weed, Disease, and Insect Management in Nebraska.

*Burndown application of Engenia/FeXapan/XtendiMax should be made only if planting Roundup Ready 2Xtend soybean.

Source: University of Nebraska CropWatch

Recent News

Fall-applied Herbicides-What Goes Around Comes Around
9/22/2020

Fall herbicide treatments have fallen off over the past several years for a couple of reasons, among them the effectiveness of new soybean trait systems for managing marestail, some generally crappy weather in late fall, and efforts to reduce input costs.  We are seeing a resurgence in some weeds, such as dandelion, which respond well […]

New Round of Farm Aid for COVID Losses Announced, and Causes Snag in Congressional Spending Bill
9/22/2020

Andrew Restuccia and Jesse Newman reported in Friday’s Wall Street Journal that, “President Trump unveiled $13 billion in new aid to farmers facing economic harm from the coronavirus pandemic as he aimed to boost support among rural voters at a campaign rally. ‘I’m proud to announce that I’m doing even more to support Wisconsin farmers,’ said Mr. Trump, speaking outside […]

Corn Silage Needs Adequate Moisture to Ferment
9/18/2020

Early season frost is challenging for corn silage producers, according to Karl Hoppe, Extension livestock systems specialist at NDSU’s Carrington Research Extension Center. Frost makes an abrupt end to the corn-growing season. This begins the dry-down period for the corn plants. “Good corn silage fermentation requires adequate moisture to reduce dry-matter loss and spoilage,” Hoppe […]

Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now