The study, a cooperative work among scientists from the University of Sheffield, Rothamsted Research and the Zoological Society of London, focused on black-grass (Alopecurus myosuroides). This highly prolific weed commonly occurs in cereal-based crops across England and a large portion of western Europe.
The researchers assessed the population density of black-grass in 70 English farms and collected seeds from 132 fields spread across these farms. In addition, the researchers also compiled historical management data. This was done to uncover the factors that could have played a role in increasing the numbers and herbicide resistance of black-grass.
Through glasshouse bioassays, they found that as much as 80 percent of the black-grass sampled was highly resistant to just about all herbicides typically used in black-grass control. The elevated levels of herbicide resistance were shown to be parallel to the density of black-grass populations. As per the researchers, this fact was indicative of the influence of herbicide resistance on the proliferation of black-grass. They noted that the intensity of herbicide use was the main driving factor in herbicide resistance, as considering all other management factors proved to have no effect.
Moreover, synthesizing different chemicals to create new classes of herbicides had no noticeable impact on the prevention of herbicide resistance, nor did the cyclical application of these new mixtures.
Part of the study also involved questioning the farmers on their use of herbicides and how much it cost them. Those farmers who had responded to higher black-grass densities by spending more on herbicides experienced significantly reduced crop yield, which in turn lead to critical profit losses. (Related: Glyphosate decreases yield, seedling quality of Roundup Ready soybeans; increases rate of fungal disease.)
According to Paul Neve, a weed biologist with Rothamsted Research, their findings should serve as a wake-up call to seek out alternative black-grass management strategies that are less reliant on chemicals.
One such alternative could be spring cropping in rotation since black-grass has been found to be less successful at affecting spring crops. Another potential solution is to lay down grass in areas where black-grass grows, at least until these plants die out. “A less palatable solution might be to put fields down to grass for a period, as blackgrass seed only survives in the soil for two or three years,” Neve explained to FWI.co.uk.
Neve further pointed out that a new hybrid variety of barley was currently being developed. This particular variety was worth noting due to its seemingly effective ability to suppress the growth of black-grass without the aid of chemicals. Yet another probable answer to the blackgrass problem was an up-and-coming combine harvester being developed in Australia, one that could crush and toss out black-grass seeds before they've had the chance to take root.
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