Soybean School: Aggressive and timely scouting boosts weed control

A cool, wet spring has slowed fieldwork and dreams of early planting appear to be disappearing as the calendar turns to May.

But the backward conditions have not stalled weed growth in fields across Ontario. That means growers will need to keep a close eye on winter annuals and mounting weed pressure in soybean and corn fields, says BASF agronomist and technical development manager Rob Miller.

On this episode of the RealAgriculture Soybean School, Miller scouts fields at BASF’s Maryhill, Ont., research site to find weeds emerging and actively growing under crop residue. “Aggressive and timely scouting is going to be key this year. We alway want to spray weeds when they are smaller and actively growing,” he says.

Some weed species, such as waterhemp, can grow up to one inch per day. “If we delay scouting by two or three days that weed has grown by two or three inches and will be tougher to control,” Miller says. Early scouting also helps ensure growers don’t end up in a situation where they have to “plant now and spray later.”

Miller notes that soil-applied, residual weed control can only be applied pre plant or pre emerge. If growers can get soil applied chemistry down early, they’ll get good control. “You don’t want that crop coming out of the ground, getting ahead of you, and the weeds coming up the same time.” (Story continues after the video.)

Miller reminds grower to also think resistance management as they roll out their weed control programs this spring. Planting is a busy and stressful time but it’s important to ensure herbicide programs contain multiple modes of effective action. This helps prevent further spread of glyphosate-resistant fleabane and waterhemp as well as weeds with resistance to multiple herbicide groups.

Reading labels and understanding rates is another key to effective control and managing resistance. Growers may be tempted to cut rates this spring because of product availability, but Miller says growers should stick to recommended rates, which are based on effective control of various weed pressures. Cutting rates can contribute to resistance as well as antagonism, specifically with glyphosate and some clay-based chemistries.

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