Soybean School: Comparing pre- and post-emerge weed control strategies


Do you need to manage herbicide-resistant weeds? Could you use more flexibility during the busy planting season? Does heavy weed pressure make it difficult to keep fields clean early in the season?

These are all questions growers should be asking as they plan their 2021 soybean weed control programs, says BASF technical development manager Rob Miller. One of the key strategic decisions growers need to consider is whether to opt for a pre-emergent or post-emergent herbicide program, or a combination of the two.

On this episode of Soybean School, Miller takes a look at an early-season weed control trial comparing pre and post systems. He notes that a good pre-emergent program can play an important role in controlling troublesome herbicide-resistant Canada Fleabane and waterhemp. And if growers don’t have these weeds, the pre option allows for more effective modes of action to keep these hard-to-control invaders at bay.

Miller says post options are effective, but application timing is critical. He notes that the critical weed-free period for soybeans extends from emergence to the 4th trifoliate stage and weed pressure during this period can impact a plant’s ability to optimize yield. (Story continues after the video.)

Miller also discusses the need for rain to activate pre-emergent herbicides. He points out that most pre products have residual activity without rain, and when the rain does come, these herbicides then offer further control of late-emerging flushes. The residual control also helps busy growers manage the spring workload and make time for other needs such as spraying wheat to control fusarium.

Whether growers are using a pre, post or a combination program, Miller does note that a two-pass application program will deliver the most consistent weed control and also give growers their best defence against herbicide-resistant biotypes.

Click here for more Soybean School episodes.

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