Corn School: Managing pre-emerge herbicides in dry spring conditions


Dry spring planting conditions have many growers wondering how their soil-applied residual herbicides will perform, as the weather continues to heat up with little meaningful rain in sight.

Research by University of Guelph weed scientist Dr. Peter Sikkema indicates pre-emergence herbicides will still deliver significant value for growers in dry spring conditions. He notes that soil-applied products typically deliver between 50 to 80 percent control even in the absence of an activating rain.

On this episode of RealAgriculture’s Corn School, BASF agronomist Rob Miller notes that full activation of the herbicide depends on the active ingredient. Some herbicides require up to 3/4″ or more for strong performance while others can make do with 4/10″. That moisture, however, needs to come in a single rain event for consistent performance and strong control of late-flushing weeds, adds Miller.

If growers do see weed escapes due to low activation, the best course of action is to accelerate the timing of a post-emergent application. To manage escapes, fields that would typically be sprayed at 5- or 6-leaf may require an application at the 1- to 2-leaf stage. Miller adds that even when the effectiveness of the soil-applied herbicide is reduced, it contributes significantly to weed control by reducing selection pressure and reliance on the in-crop herbicide. (Story continues after the video)

Overall, Miller is advising growers to “stay the course and manage the crop, not the weather.” He says it’s not only important to control weeds this year but also take an integrated management approach where controlling weeds in the corn crop will set growers up for success in following soybean and wheat crops.

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