Soybean School: Controlling lamb’s quarters and other broadleaf bullies

As soybeans move through the early vegetative stages, it’s time for growers to tackle those broadleaf weeds and grasses that might have evaded soil-applied herbicides or emerged after burndown.

On this episode of the RealAgriculture Soybean School, BASF agronomist Rob Miller and host Bernard Tobin talk strategy in a weedy field of 1st trifoliate soybeans near Guelph, Ont.

Miller takes specific aim at lamb’s quarters and the need to control the weed in conventional and identity preserved soybeans. In this field, which received a burndown treatment only (no residual herbicide was applied), lamb’s quarters, ragweed and pigweed are muscling in on the fledgling soybean plants.

“It’s definitely been a lamb’s quarters year,” says Miller. He recommends growers get out and look for the weed because a waxy calcium deposit on the leaves can make it difficult to control. “That’s why it’s really important to get out there and scout because this waxy calcium deposit can actually inhibit the spray droplets, and not allow [herbicide] to penetrate these weeds.” That can make the weed very difficult to punch out, especially in some IP soybeans. (Story continues after the video.)

Miller notes that the dry conditions that had persisted throughout the spring have created some variable plant stands, which could lead to a slower-developing canopy that may not deliver the ground cover required for effective weed control. “They’re going to start flowering in about three weeks from now so the window is actually closing very quickly in terms of those conventional herbicides that we can apply with residual.”

Without a sweeping canopy, many fields will need residual help to keep weeds under control throughout the season, especially if rain arrives and triggers a big flush of weeds, adds Miller.

In the video, Miller shares several best practices, including tips on when to spray during the day and what conditions contribute to higher efficacy — spraying in the middle of a hot day is the best combination for better weed control. He also discusses the need to pay close attention to adjuvants, water volumes, tank mix choices and the potential for antagonism when combining products.

Tap here for more Soybean School videos.


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