blackgrass

Herbicide resistance is the inherited ability of a weed to survive a rate of herbicide which would be lethal to a member of the normal population. It can develop over time based on repeated selection pressure imposed on the weed, this selection pressure changes the population from susceptible to resistant.

 

Herbicide resistance is genetic within the plant and should not be confused with poor herbicide efficacy (e.g., poor weather, timing of application, spray quality, spray conditions etc.). Symptoms can include healthy plants beside dead plants of the same species, a susceptible species having poor control when other susceptible species are well controlled, discrete weed patches and a general decline over a number of years. The two main types of resistance mechanisms include target site resistance and enhanced metabolism

So far in the UK resistant populations of weeds have been found in:

  • Grasses
  • Black-grass
  • Italian-rye grass
  • Wild oats
  • Broad leaved weeds
  • Poppy
  • Chickweed
  • Mayweed

Resistance has also been found by ADAS in an ALS resistant prickly sow thistle

Herbicide resistance tests are key to confirm resistance and help future management of resistant weeds by choosing the correct chemistry. These can be done by collecting seed from suspected resistant weeds and sending to ADAS who will test the seed for its resistance status.

 

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Integrated Pest Management highlights the growth of a healthy crop with the least possible disruption to agro-ecosystems and encourages natural pest control mechanisms.  

A weed can have many definitions, one being, any plant growing in a place it is not wanted.

Black-grass (Alopecurus myosuroides) is a major weed in winter sown cereals.

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The Weed Resistance Action Group (WRAG) produces guidance on pesticide resistance issues. Hosted by AHDB, this information can be used to help protect crops and the long-term efficacy of herbicides.

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