Avoiding Herbicide Resistance in Weeds

A wise farmer once said, “If you do anything the same way long enough, it’s wrong, because soon things are going to change”

This is certainly true when speaking of weeds and herbicide resistance.

Just like any other farmer, cereal growers in Africa have their challenges especially on weed control and management.  A reoccurring challenge has been on weed resistance.

“One result of modern agriculture and its reliance upon herbicides is the emergence of weed populations that are resistant to herbicides”,   “We want our farmers to be informed on new farming techniques. To us, this is more than just selling a few bottles of herbicides. Growers need to think ahead, to think smart. We are here to walk with them as they grow their crops”,

Weed Resistance

This is defined as the inherited ability of a weed or crop biotype to survive a herbicide application to which the original population was susceptible.

Factors that influence the Evolution of Resistance

  • Using a herbicide with the same mode of action.
  • Using the same herbicide multiple times during one growing season.
  • Repeated application of a herbicide with the same mode of action.
  • Chemical strategy (Herbicide used without other weed control strategies).
  • Repeated use of a product for more than 2 years could develop a herbicide resistance challenge.
  • Use of lower application rates
  • A monoculture of continues wheat/maize production
  • Weeds that produce lots of seeds with little dormancy and short longevity
  • A herbicide that has a high efficacy on a specific weed species
  • A herbicide with prolonged residual activity
  • Use of lower that recommended rates


In a discussion with the farmers, its explained that avoiding herbicide resistance is the preferred route for this problem. However, if herbicide resistance has already arrived, recognizing and properly managing herbicide resistance can save some tremendous weed headaches.

Here are some recommended solutions for farmers:

  1. Prevention is better than cure- Don’t wait for herbicide resistance to occur.
  2. Map out resistant weeds in your farm
  3. Focus on a spray regime to take out resistant phenotypes
  4. Observe application timing and rates as recommended on the label
  5. Chemical Mode of Action rotation
  6. Split application of herbicides for BLWs and grasses
  7. If herbicide resistance is suspected get expert help immediately