Consider residue risk when planning spring PGRs

Pesticide residues in grain and cost-effective cooling strategies were top of the agenda at a HGCA grain storage workshop in Essex last week.

Stricter EU legislation and changing consumer attitudes towards food quality mean cereal growers will have to do more to reduce the risk of pesticide residues getting into grain, Martin Gibbard, adviser to the Assured Combinable Crops committee, told delegates.

The Pesticides Residue Committee’s quarterly reports regularly found small residues of four active ingredients in cereals and although legal Maximum Residue Levels (MRLs) had rarely been exceeded, public perception meant more would have to be done to cut residue risk, he said.

“It’s certainly not a safety issue, as the MRLs are rarely exceeded, but it’s the frequency residues occur that gets the attention [see table]. Some markets, such as brewers, distillers, baby food producers and some breakfast cereal companies, are already asking for residues to be minimised. The cereals sector won’t go as far as fresh produce has, but it will move in the same direction.”

For cereals, the four main actives involved are chlormequat, mepiquat, glyphosate and pirimiphos methyl.

Mr Gibbard said in all cases, growers should review cultural and management options before using chemical products, but where they were needed, a few simple actions could reduce the risk of residues occurring. “All we’re talking about is refining what you do within label recommendations.”

For the growth regulators chlormequat and mepiquat, that mainly related to application timing. “Try to move timings forward to the front end of recommendations.” For stem shortening in wheat using chlormequat this meant applying at growth stage 30, rather than GS32, he suggested, while for mepiquat treating at GS33-37 would balance efficacy with minimising residues.

“But remember crops must be actively growing and spring crops rapidly move through growth stages. Also, some may not be able to get on earlier due to difficult travelling conditions.”

The biggest problems from glyphosate came from using it pre-harvest, Mr Gibbard continued. “Don’t apply until 30% grain moisture is reached. Earlier applications will give significantly higher residues.”

He advised growers to keep to the minimum rate (1 litre/ha of a 360g/litre formulation) and to abide by the seven-day harvest interval. “High rates tend to bring residues through.”

For pirimiphos methyl he said good store hygiene prior to filling and moisture and temperature management were key to avoiding the need for chemical treatment.

Example PRC report, Q3-4, 2006


MRL (mg/kg)

Residue detected (mg/kg)

% samples containing residues


2.0 (wheat, barley, rye)




2.0 (wheat, barley, rye, triticale)







Pirimiphos methyl

2.0 (flour, 0.5 white and 1.0 wholemeal bread)




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