Weed the world

Glyphosate, while not without its detractors, has become a byword for weed control. However, reliance on one herbicide is a ticking time bomb, says tim Field

It is used in tree planting and establishment; to prepare a seedbed before drilling; to establish wildflower plots, conservation mixes and cover crops; to control Japanese knotweed and other invasive species; to desiccate foliage before harvesting; to maintain electric fences for game or livestock… the list goes on. Glyphosate is the top-ranked herbicide in Britain and 650,000 tonnes of it are applied globally each year. Not surprisingly, a flurry of negative attention around it is alarming for farmers, land managers and consumers. It even carries a trending hashtag, #glyphosateisvital.

the yellowy-brown remnants of wizened stems confirm that glyphosate has cast its spell. A highly effective, broad-spectrum herbicide since it was brought to market by Monsanto under the trade name Roundup in 1974, many farmers now claim to be dependent on it so recent legal wrangling will be of great concern to them.

Whilst there are hundreds of scientific papers used by the crop-protection industry to claim the safety of glyphosate, there have been a few outlying studies and mainstream organisations that raise doubt. the bestknown was a widely discredited research trial by French molecular biologist Gilleseric Séralini in 2012, which investigated Roundup toxicity in rats. He claimed his longer trial period had revealed incidences of tumours in rats fed with Roundup. the French-based International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), said in 2015 that glyphosate was a “probable human carcinogen”. However, this was at odds with a joint report by the WHO and the UN in 2016 saying glyphosate, “is unlikely to pose a carcinogenic risk to humans from exposure through the diet”. In 2017, there was enough concern in the EU that a proposed 15-year licence for glyphosate use was reduced to just five years.

Although there is no raging fire of evidence linking glyphosate to cancer, there is enough smoke to build a case. A court in America has ordered Bayer-owned Monsanto to pay £226m in damages to a terminally ill school groundsman. Bayer has vowed to appeal; however, it is reported to be facing several thousand more law suits and share prices have plummeted.

Even if, say, creosote or cigarettes were found to pose a greater cancer risk, we are largely in control of our contact with them, whereas, unless buying organic produce, glyphosate is detectable across a large range of foods eaten worldwide every day. A US study found it arose in the urine of more than 90% of the pregnant women tested.

Aside from the public health furore, glyphosate is becoming a victim of its own success. Outside the EU, where Monsanto’s Genetically Modified (GM) seeds mean Roundup can be sprayed on a crop killing the weeds only, the selection pressures of constant and widespread glyphosate application resulted in resistance and ‘super weeds’. the UK’S restrained adoption of GM seed means glyphosate resistance has not arisen here, however, such dominance by one herbicide is a ticking time bomb. We already see financial and ecological challenges through herbicide-resistant black-grass.

Alternative, non-chemical methods of weed control are wide and varied. Ploughing, crimper rolling, harrow combing, false seedbed, blind harrowing, bastard fallow and extended rotations all act to interrupt weed establishment, whilst variety selection and good timing can negate the need for pre-harvest desiccants. Organic farms are not allowed to use herbicides so our own recent tree-planting project in the chicken ranges used woollen mulch mats to suppress weeds. Even with mulch mats, the best trees established where chickens scratched out the weeds, suggesting more mowing and strimming would have been desirable. In the market garden, the use of mulch sheets, hand weeding and elbow grease are resource intensive but dependable options.

Minimum tillage methods are largely dependent on glyphosate, so proponents will claim to be at a loss and argue adverse consequences on soil health, biodiversity and carbon emissions without glyphosate. However, many progressive farmers are already talking of a future where the herbicide is restricted and are beginning to plan cultivation techniques to be ahead of the chemistry alternatives. Whether alarmed by public-health risks or resistant weeds, nobody can deny we are too dependent upon one weapon for weed control and that cultural change is required.

Follow Tim and Agricology, @agricology

Glyphosate is detectable across a large range of foods eaten worldwide every day