What is pre-harvest desiccant use of glyphosate?

Glyphosate is the world’s most popular weedkiller   

Glyphosate is a broad-spectrum herbicide and the most heavily used pesticide globally. It’s applied year-round as a weedkiller on many farms - despite growing evidence of its impacts on human health and wildlife.   

In the early 1980s, farmers in the UK discovered glyphosate could also be used as a pre-harvest desiccant. Crops are sprayed shortly before harvest to dry them evenly, ready for the combine harvester. The practice spread through northern Europe then worldwide, helping farmers beat autumn rainfall, plan harvests in advance, and meet food system demands for speed and uniformity.   

Before its use as a desiccant, weed control practices rarely resulted in residues in harvested foods. Pre-harvest spraying changed that - meaning glyphosate residues don't have time to dissipate before harvest. Now, they're regularly found in commonly consumed everyday foods such as bread, breakfast cereal and beer.   

In the UK, summers are often wet and crops may ripen unevenly, and this is part of the reason glyphosate is so widely used. Now pre-harvest use accounts for approximately 30% of the usage in wheat and barley and 59% in oilseed rape.   

Pre-harvest spraying leaves residues in our food   

Independent monitoring of UK grown wheat, barley, oats and their co-products revealed glyphosate to be the second most common pesticide residue per sample. 442 samples of 1075 (41%) samples contained it.  UK Government data backs this up, showing that glyphosate residues are common in starchy and cereal based foods.  

These residues rarely exceed the so-called Maximum Residue Limits set by government. However, a growing body of research indicates that glyphosate might be more harmful than previously assumed. This implies that stricter regulation is needed, including drastically lowering Maximum Residue Limits and introducing usage restrictions, including for pre harvest desiccation.   

Glyphosate is found in the human body  

Although only limited data is available for the UK, a 2022 study found glyphosate in the urine of 99% of the French population. Higher levels were found in men, children and farmers. A US study found glyphosate in the urine of more than 90% of farmers and over 80% of non-farmers. This is likely the result of both dietary and environmental exposure. 

Many farmers don’t use glyphosate pre-harvest  

Managing crop drying and harvesting without glyphosate is likely to be challenging for some farmers, but there are mechanical, biological, and agronomic alternatives that can be adopted, with adequate support from government and the supply chain. These include swathing (cutting and drying crops in a field), grain dryers stripper headers, and monitoring tools.   

The best approach depends on the farm system, the crop, and the ecological context. While there might be trade-offs in yields and emissions, organic farming shows that with right support and innovation it’s entirely possible to produce crops without glyphosate. 

In 2015, the Soil Association launched Not in our Bread- a campaign urging UK bread companies and major retailers to stop using wheat treated with glyphosate pre-harvest. Our concerns about this practice remain. We continue to call for support from government and innovation to move all farmers away from reliance on pesticides, which damage human health and the environment.