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 Narok 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”, states Doris Kawira, Amiran’s  Cereal Manager.

During a dinner hosted by Amiran Kenya and Dow Agro science, large-scale farmers in Narok were taken through a detailed training on how to prevent weed resistance.  “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”, explains Oscar Shilliebo from Dow Agroscience.

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, Oscar 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

A drive around the farms in Narok County not only links one to nature as you enjoy the green serenity but also makes one appreciate the effort and handwork of the maize and wheat farmers in the area. Farming is taken very seriously in Narok County by both small and large scale growers. During the growing season the county is busy with activity; planting, crop nutrition and protection spraying, harvesting, sorting, the list is endless.

Partnerships that bring together like-minded organizations such as Dow and Amiran have the farmer at heart, as their experts spend their days researching, conducting trials and coming up with modern farming practices that are ideal for cereal farmers, all with the end goal of ensuring farmers have an easier time at the farm and a smiling face when cashing in their returns.