Pest Patrol: Weed control update on vetch

Can I do anything to get rid of vetch before seeding soybeans?

In my last column, I discussed my optimism for vetch control in soybeans using a few different pre-plant burn-down herbicides.

Specifically, I had been impressed by some preliminary results when either flumioxazin (found in Valtera, Step-Up, Fierce and Guardian Plus) or saflufenacil (found in Eragon, Integrity and Optill) was mixed with glyphosate and the adjuvant Merge.

I promised to provide an update on the level of weed control because I wasn’t completely convinced that the control we saw early in the season would last. Past experience has shown that when herbicides that burn leaf tissue quickly are tank mixed with glyphosate, perennial weeds tend to grow back quickly.

Although the treatments discussed above provided impressive burn of any emerged vetch at four weeks after application, the vetch did grow back at eight weeks after application.

However, there was an unexpected silver lining in this trial. The addition of 2,4-D ester 700 in burn-down treatments, although somewhat unimpressive at first, provided better control of vetch than any other treatment at eight weeks after application.

Bottom line: 2,4-D ester 700 applied pre-plant in soybean looks like a promising tool for the control of vetch in soybeans, provided vetch has emerged at the time of application. More trial work will be needed to verify the consistency of these results.

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