The Importance of Residual Herbicides



Herbicides--commonly known as weed killers--can work their weed-controlling ways for varying amounts of time. The length of time that an herbicide is effective is known as its residual. Herbicides with long-ranging effectiveness that are applied after planting but before crop (and weed) emergence are called residual herbicides, referring to their longevity.

Weed Resistance and Residual Herbicides

With weed resistance on the rise, residual herbicide usage is taking on increased importance. Using residual herbicides with several Modes of Action (MOAs) can increase the probability of acceptable weed control by giving the crop a longer time to emerge and reducing resistance pressure on post-emergence herbicides.

Residual herbicides can be especially important in fields that already have herbicide-resistant weeds. These residual herbicides are selective, meaning they control certain weed species while leaving the crop being grown unharmed. They should be applied before weeds emerge. Get more information on making the most of your chemical applications.


How to Use Residual Herbicides

Residual herbicides control weeds by root, shoot and seed absorption, and persistence varies between products. Therefore, selecting the correct herbicide to match the target weed’s emergence pattern is important. It is often necessary to apply an additional residual herbicide at post emerge to adequately control certain weed species that have an extended germination period.

You should also consider replant options and rotational restrictions when selecting a residual herbicide. Replant options generally come into play following a weather event that destroys the existing crop. Rotational restrictions refer to future plantings or planned crops to be grown. Make sure that the residual herbicide you choose meets your future plans for the land where you plan to use the herbicide. This information can be found on the herbicide label--

You can view hundreds of herbicide labels at 

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