4 ways to prevent herbicide resistance

Resistance is a naturally occurring, inheritable ability of individual plants within a given weed population to survive treatment that would otherwise control that population.

A small number of plants in any population can be assumed to be naturally resistant to a particular herbicide. Repeated applications allow them to survive, set seed, and, over time, dominate the population.

The threat is severe enough that suppliers formed the Herbicide Resistance Action Committee (HRAC) (www.hracglobal.com). According to the HRAC, more than 150 herbicide-resistant weed biotypes have been recorded in about 50 countries.

So far, none have become completely ineffective. To keep things that way, HRAC’s Guidelines to the Management of Herbicide Resistance recommends an integrated approach that combines the following techniques:

1. Use multiple herbicides with different modes of action that affect overlapping weed spectrums. Apply the herbicides in rotation, sequences, or mixtures.

2. Use the herbicides at the full recommended rate, and time the application for the weed species that are the most difficult to control.

3. Scout the area after application to make sure control has been achieved. Don’t allow weeds to reproduce by seed or to proliferate. 

4. Monitor the site and clean equipment between sites.

- Kenneth A. Hooker is a freelance writer in Oak Park, Ill.