A ten-minute chat with Sarah Cook, weed biologist from ADAS.

10.07.2019

The black-grass battle bus is on the road, and has already visited some fantastic demo days up and down the country. On the bus you will get a chance to speak to some of our experts. On a rainy day on the 3rd June, we had a spare ten minutes to talk to Sarah Cook on board the bus about black-grass resistance.

Why test your black-grass grass?
Well, very simply, so you can get the greatest efficacy out of the herbicide you are using.

What trends have you being seeing when it comes to black-grass resistance?
It’s not good news to be honest. We’ve seen increasing resistance to herbicides in all modes of actions, in target site and enhanced metabolism, but never glyphosate.

What’s caused the increase in resistance?
Again, the answer is relatively simple, over reliance on single groups of herbicides. We’ve had resistance to herbicides for a long time, and over the years we’ve let it get out of hand by not focusing on integrated methods. The attitude towards weed management is starting to change out of necessity, and it is positive to see so many growers and agronomists promoting best practice.

It is however understandable, weed control is complicated, it takes a sustained effort and attention to detail at every stage to ensure sustainable control. Herbicides are not like fungicides, there is no magic single hit control, we’re now seeing a nation-wide change of mindset towards weed control and that can only be a good thing.

If someone is worried about resistance on their farm, what should they do?
Have a resistance test, so we can pinpoint exactly what type of herbicide your black-grass is resistant to. A move to pre-em and focus on different methods of control are vital, it takes a lot more planning, but the effort does pay off.

Once you have resistance it can only get worse, it never gets better, so a reluctance to change practices or bury your head in the sand will only result in a greater level of resistance.

In 2013 you worked with BASF to give away resistance tests, and we’re doing the same this year. What do you expect to find out?
Last time we found that 50% of growers had the three types of resistance, and I expect that to rise. I am very interested to find out how rotation and cropping has had an impact on levels of resistance.

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