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Glyphosate – be aware of contamination risks and get safe application guidance

21 June 2013

Glyphosate is a non-selective herbicide used by most farmers. Its use has increased extensively in the last 10-15 years, particularly as a harvest aid for cereal crops and oilseed rape. It can be an effective solution for potato growers, especially for pre-plant control of weeds and volunteer grains.

What many growers don’t know is that glyphosate contamination can cause significant damage to seed potato crops, even at very low concentrations.  Drift, tank contamination and misapplication during the growing season can seriously reduce the yield and quality of potato crops, and the effects on seed potatoes can be found well into the following year.
Contamination often isn’t noticed until the seed crop has been sold and re-planted, causing commercial disputes that often take several years and large sums of money to resolve. This could have negative consequences for the reputation of British seed 
Glyphosate contamination occurs in two main ways:
  1. A sprayer used for glyphosate application that is cleaned poorly, and subsequently used to spray seed potatoes; 
  2. Drift from neighbouring crops being sprayed with glyphosate.
Potentially the most serious is number 2 because damage is often un-noticed, and can involve non-potato growing farmers. In fact, the most common cause of glyphosate contamination is spray drift, usually from a neighbouring oilseed rape or cereal crop receiving a pre-harvest spray.
Seed potato growers should start building a glyphosate risk awareness programme now to help protect their crops from accidental but potentially costly contamination during the spraying season in July, now rapidly approaching.
Rob Burns, head of seed and export at AHDB Potatoes advises that “Glyphosate is a non-selective weed-killer which is incredibly damaging to seed potatoes. Even at levels which cannot be detected, it can cause horrendous problems with germination and emergence in the daughter crop.” Problems are most likely to occur when crops are grown on rented land, he adds. “The landlord may not be aware of the risks of glyphosate on a neighbouring seed potato crop”.
“Typical spray drift effects can reduce emergence to just 25-30% of normal, and in the worst cases it can be as low as 5%”. Rob warns that “The biggest risk of contamination occurs in July so it’s now that growers need to know which fields will be sprayed and what’s surrounding them.”
“The use of alternative, safer desiccants or no-spray zones in fields bordering susceptible seed crops are also worth exploring” he adds. “Our suggestion is that potato seed growers should talk to their neighbours and find out if they plan to spray glyphosate. A conversation or two now could save a lot of problems further down the line.”
AHDB Potatoes has a guidance leaflet and in-cab sticker set warning of the risks when spraying glyphosate near vulnerable seed potato crops and which gives specific advice on safe application of the chemical onto target crops.
“We have glyphosate guidance available for seed growers to hand out to local growers, sprayer operators, neighbours and contractors. You can pick some up at any of our Potato Days or just ask us to send you some to hand out. It all helps”, says Rob.
For AHDB Potatoes guidance leaflets and stickers on glyphosate, visit: or email
Webcast: View webcast on the effects of glyphosate on seed potatoes, given by Dr. Andrew Robinson, Assistant Professor and Extension Potato Agronomist at North Dakota State University and the University of Minnesota. Available online until 31 August 2013.
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