Glyphosate - the Debate

What is glyphosate? Should it be banned? And how can you manage weeds without it?

Glyphosate is a toxic herbicide used to kill weeds. It is not acceptable in organic growing.

Here are 10 things you need to know about glyphosate:

  1. Glyphosate is rarely used on its own, but as part of a chemical cocktail, for instance with the trade name Roundup or Weedol.
  2. These formulations are potentially far more dangerous. Dr Robin Mesnage of Kings College London, writes "We know Roundup, the commercial name of glyphosate-based herbicides, contains many other chemicals, which when mixed together are 1,000 times more toxic than glyphosate on its own."
  3. The European Food Safety Authority (EFSA) says that glyphosate is safe. However, most of their research is provided by the industry which created the herbicide. They haven’t tested the various individual commercial formulations. And regulation safety tests on mammals cover a short period, maximum 90 days. No-one knows the effect of longterm exposure to these toxic chemicals.
  4. This is worrying, because independent research indicates that glyphosate is not only possibly carcinogenic, but that it also affects the body’s endocrine system – causing problems in the liver and kidneys. Industry testers dispute this, but interestingly have declined to reveal all the results of their safety tests. See Corporate Europe report.
  5. Over 30% of the bread in the UK contains traces of glyphosate. While not necessarily toxic in small amounts, this gradual and persistent intake could create a health risk.
  6. This recent paper explores the effect of GBHs (glyphosate based herbicides) on the human gut. Interference with gut enzymes gives rise to many diseases such as gastrointestinal disorders, obesity and diabetes.
  7. Glyphosate is the most widely and heavily used agrichemical worldwide, in agriculture, parks and amenities as well as in gardens.
  8. Recent research shows that glyphosate formulations destroy the micro organisms in healthy soil, and affects earthworms. (For a full review of the research of glyphosate on soil ecosystems, see this 2016 report from the Soil Association.)
  9. Glyphosate producers claim it is rapidly inactivated in the soil. However, the chemical is very persistent in soils and sediments, and in colder, seasonal climates, such as the UK, residues have been found in the soil for up to 3 years. It also inhibits the formation of nitrogen-fixing nodules on clover for up to 4 months after treatment.
  10. Again, makers of glyphosate claim that it is unlikely to pollute the water (ground or surface). However, a recent paper from San Paulo State University, Brazil, shows that glyphosate formulations profoundly affect the algae in fresh water. Researchers have found traces of glyphosate in wells, ground waters and reservoirs across Europe and the UK. Water contamination is probably as a result of drift from spraying, or from soil run off and erosion.

So how does this toxic chemical work?

Glyphosate is absorbed through foliage, inhibiting the plant’s ability to synthesize proteins. This causes it to sicken and die.

Monsanto has genetically engineered crops such as soya, corn and wheat, to be resistant to glyphosate, so that when sprayed they survive - but the weeds die. However, after years of use, this has created resistance in the weeds, so called 'super weeds'. Depressingly, it appears the only way to treat these resistant weeds is to use yet more chemicals.

Should glyphosate be banned?

Garden Organic strongly opposes the use of toxic chemicals ... to use glyphosate formulations, such as Roundup, is to poison the soil, the wildlife and ourselves. It is totally contrary to our organic growing beliefs.

The World Health Organisation listed glyphosate as probably carcinogenic. Numerous other independent research studies have looked into the chemical's negative impacts. These include damage to liver, kidney and skin cells, as well as disruption to soil and aquatic life.

However, the European Food Standards Agency (EFSA) claim that "glyphosate alone is not dangerously toxic to humans or animals." Their opinion is based on a limited number of scientific studies, many of which are industry led. Similarly, the UN’s Food and Agriculture Organisation (FAO) found that the chemical was “unlikely to pose a carcinogenic risk to humans from exposure through the diet”. This omits the effects of topical application of glyphosate for farmers, and those who live near sprayed fields and parks. Neither does it look at other illnesses potentially caused by the herbicide, nor does it examine the other chemicals mixed with glyphosate, which have greater toxicity, and are potential endocrine disrupters.

The licence for glyphosate use in the EU has recently been under discussion. After a long battle between the agrichemical industry, who wanted a full 15 year renewal, and concerned environmental NGOs and individuals, who wanted glyphosate banned - a licence has been granted. But only for 5 years. The EU Commission also added certain recommendations for its use: to ban the co-formulant, POE-tallowamine; to reinforce scrutiny of farmer's use of glyphosate just before harvest; and to minimise its use in specific areas, such as public parks and playgrounds. To date it is unclear if the UK government is prepared to accept these recommendations.

See here for an analysis of the responses to this licence renewal.

How to deal with weeds without a glyphosate cocktail

To grow organically is to cultivate plants without artificial chemicals - especially those that are toxic and damage wildlife.

However, some growers still feel the need to control weeds in their paths and hard surfaces by killing them with glyphosate. This is not an acceptable organic practice. So what advice can we give? From path preparation to mulches and organic weedkillers, here are some ideas.

See also Weed management

Preventing weed growth on hard surfaces

  • Lay your paths and hard surfaces with an impenetrable foundation layer: a geotextile membrane or a substantial mix of hardcore rubble and sand, firmly flattened to exclude all light and reduce moisture.
  • Cracks between pavers should be filled with mortar - not sand, which provides the ideal medium for weeds to germinate. Lime mortars are more environmentally friendly than cement mixes.
  • Existing hard surfaces with persistent weeds can be treated either by manual removal, boiling water, or by a thermal killer. These instruments provide directed intense heat to kill the plant shoots. It is effective particularly on young weeds, and if used twice in the growing period.

For a comparison of weed killer methods (thermal, hot water and Glyphosate) see http://www.regional.org.au/au/asa/1998/6/315hewitt.htm

Mulches for growing areas

Weeds will occupy an area of soil where nothing else is growing. To prevent this happening, cover the soil between plants so that light cannot penetrate. This is called ‘mulching’. Mulches can be made from a thick layer of organic matter (compost, shredded bark, cardboard, newspaper, straw etc) or from sheets of plastic textile. A compost mulch is ideal, as not only does it suppress weeds but it also feeds the soil beneath and improves its texture.

Organic weed killers

These contain pelargonic acid (a fatty acid). They only kill top growth, usually the roots are not affected.

Organic weed killers are available online. Members of Garden Organic will get a 10% discount at The Organic Gardening Catalogue. Phone 02476 308210 or email membership@gardenorganic.org.uk to find out how to become a member.

References and further reading

Friends of the Earth, Health and Environmental Impact of Glyphosate 2001 report

IARC report classifies glyphosate as probably carcinogenic

Pesticides Action Network Fact sheet and Alternative Methods of Weed Management without glyphosate for farmers.

Organic Weed Control by Pauline Pears. Pauline’s article is from the magazine The Organic Way (Autumn 2015, ed TOW214), available only to Garden Organic members. If you would like to become a member, phone Garden Organic on 02476 308210 or email membership@gardenorganic.org.uk.