When Herbicides Fail

There’s no magic bullet to weed control.  No matter how much you work toward fighting unwanted weeds, resistance continues to build and spread.  Zack Trower, Agronomist with Syngenta, says it’s important to make the most of your weed control program.


“When we talk about some problems that guys are seeing, I generally break it up into two sections. We have guys that run one-pass pre- programs and we have two-pass programs. The problems with the one-pass pre- programs are generally, it’s a high-pressure field and we’re seeing some breaks on the back side. With the two-pass programs, especially in soybeans in the past few years, what we’ve seen is we just haven’t been controlling the weeds on that second pass of burning them down.”


There are many reasons a herbicide may not work, but Trower said there are a few common things to look for, including a herbicide applied at the wrong time.


“When we apply our pre’s, we got to make sure that we’re getting them as close to planting as possible. Obviously, if there’s a restriction with the crop being up, we want to make sure it’s on before the crop is up. When we talk about our post- application, we really want to get the post on before any weeds are up if we’re relying on residual control, or we want to control them before the tallest weed is 4 inches in the field.”


Trower said that herbicides are made to target specific weeds and that growers need to make sure they’re using the right herbicides for the weeds in their fields.


“Another big problem is the wrong herbicide being used on the wrong weed species. We really have to know what’s out in our field and work with a retailer or a Syngenta sales rep to find the solution customized for your farm. Finally, when we create a program, we have to make sure it has multiple effective sites of action.”


He added having multiple effective sites of action is important to help reduce the possibility of resistance building in a particular weed species.


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