Late to the field? Your herbicide application rates may be affected

How a late start will affect application rates

How timing affects herbicide application rates

A wet start to crop planting and growing seasons — like the one farmers in many parts of the country have faced this year — has created several herbicide application issues that could lead to weed control challenges later on.

Excessive moisture in the form of both snow and rain turned fertile fields into lakes earlier this spring, with some areas facing massive and costly devastation to land and crop infrastructure. Beyond that high-profile damage, excess moisture has cranked up the pressure for farmers to get everything done in the field — fertilizer applications, tillage, planting and herbicide applications — before the clock runs out.


A pair of weed control problems

Those conditions have caused one of two weed control problems for farmers entering summer. First, farmers were pressed for time and were unable to get pre-emergence herbicides applied before planting. Secondly, others encountered wet conditions after planting when post-emergence herbicides would normally be applied.

If you’ve faced a general delay in applying herbicide, it’s likely your crop — and the weeds you’re targeting — will be further along developmentally. This will make it critical to account for that development through scouting and checking herbicide labels before turning a wheel on your sprayer.

“Wet weather can result in weeds and crops that are larger and more advanced in growth stage than anticipated,” according toa reportfrom Ohio State University Weed Management Specialist and ProfessorMark Loux. “The larger crop is primarily a problem in corn, where a more advanced growth stage can start to limit herbicide options.”

Herbicide application rates dependent on spraying crops and weed control

Rates may need to be adjusted based on the size of both your crop and invasive weeds, as well as any correlated changes in plant uptake of applied chemicals.

Loux说,由于降雨而延迟的开始通常需要增加除草剂的施用量,特别是在Roundup Ready和LibertyLink领域,而一些通常只使用草甘膦就能很好控制的草可能需要额外的clethodim产品。在巨型豚草和其他杂草大量生长并表现出抗除草剂迹象的情况下,建议施用最大推荐率。也可以考虑混合其他标记为控制杂草的产品,如大豚草,添加到全率的草甘膦应用。

Though he recommends full rates and potentially adding a residual product if applying herbicides late, especially in soybeans, Loux said it’s important to observe the required re-crop interval. This will prevent any unintended residual adverse effects on next year’s crop.

“While we advocate strongly for the use of residual herbicides in soybeans, the need for full rates of residual premix products applied in late June is debatable. Some residual herbicide labels specify a 10-month or greater interval between application and corn planting next year; and we are through the period of peak weed emergence, so the residual herbicide activity does not have to last as long, assuming that post herbicides will be applied,” Loux said. “In addition, soybeans grow more rapidly when planted in late June compared with early May, so there is less time until a crop canopy develops to help with weed control.”

In general, it’s critically important in examining both primary and alternate pre- and post-emergence herbicide options to closely read product labels to ensure you’re both applying a product that will be effective and preventing any unintended residual effects that could harm crop output potential in the short and long term.

If you’re facing wet spraying conditions this spring,here’s more helpto make sure you’re spraying the right way.

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