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Don’t Skimp On Herbicide Rates This Spring

May 6, 2019
Agronomic image of marestail in corn field

Herbicides for your fields are a lot like antibiotics when you’re sick. Always take the full dose for as long as the doctor tells you. If you don’t, you risk the infection still being in your body, now with a built up defense against the antibiotic.

Using reduced herbicide rates does the same thing.

The cut rate may harm the weed, it might not be strong enough to kill the weed. The weed could bounce back, but this time it could have a defense against the herbicide, and any seeds it produces will have that same defense. Weeds need to be fought with full herbicide applications to help crops grow strong from planting through harvest. Cutting herbicide rates is a technique that has traditionally caused more harm than good for growers’ fields.

As noted by the Iowa State University Extension, using partial rates may be effective early in the season; however, the length of control later in the season is negatively impacted. Partial rates result in less residual control of weeds and can shorten the window for post-emergence applications. It can also accelerate the risk of herbicide resistance developing in a field, as more applications are needed to kill weeds.

History has shown that weeds have the ability to build immunity when repeatedly sprayed with the same herbicides. In addition to spraying full rates, we recommend growers use multiple sites of action to keep fields free of weeds. Putting the time and money in up front will ultimately have a positive economic impact on farms, as crops will be healthier and additional money will not have to be spent to respray fields.

Boundary® 6.5 EC or BroadAxe® XC herbicides followed by Flexstar® GT 3.5 or Tavium® Plus VaporGrip® Technology herbicides will protect soybeans from a number of key grass and broadleaf weeds. Boundary 6.5 EC can also be used pre-emergence before applying Prefix® herbicide early post-emergence. With timely applications, these systems provide overlapping residual control.

Corn growers can rely on Acuron® or Acuron Flexi corn herbicide followed by Halex® GT herbicide to manage weeds. This program can be split into a 2-pass system with a foundation rate applied at pre-emergence and the remaining rate applied post-emergence.

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