'Weed threat greater than before herbicides'

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CROPS are now more vulnerable to weeds than before the advent of herbicides, according to a new study.

Using data from a long-running experiment, a team from Rothamsted Research has found that, on plots where herbicides have never been used, yield losses to weeds have been consistently increasing since the 1960s.

Less than a third of a harvest was lost to weeds in the first 10 years of the dataset, but between 2005-2014, this rose to more than half. The team from Rothamsted Research who carried out the study, say this is due to weeds doing better than crops in a warming climate, coupled with a shift towards shorter crop varieties that get shaded out by taller weeds.

And just like our crops, many weed species have also benefited over this period from increased use of nitrogen fertilisers.

In addition, more than half a century of consistent chemical spraying has also led to the rise of herbicide resistant weeds, threatening our ability to protect the gains in crop productivity achieved since the 1960s.

Lead author Dr Jonathan Storkey said: “Reducing yield losses from weeds is increasingly challenging because of the evolution of herbicide resistance and we can no longer rely on herbicides alone to counter the increasing threat from weeds. 

“If we compare yield lost to weeds in the first 10 years of the dataset weeds ‘robbed’ on average 32% of the yield compared to 54% in the last 10 years of data. Our results demonstrate that weeds now represent a greater inherent threat to crop production than before the advent of herbicides and integrated, sustainable solutions to weed management are urgently needed to protect the high yield potential of modern crop varieties.”

The study is published in the journal Global Change Biology.

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