New Label Instructions for Diuron

With the demise of atrazine and simazine in the non-agricultural weed control arena, the residual herbicide diuron has been intensively marketed as an alternative (see PN 24 p.17), and is now contaminating drinking water.

According to the latest annual report from the Drinking Water Inspectorate for England and Wales, diuron is the fourth most frequent pesticide found to contravene the legal contamination levels in drinking water, with a total of 3906 contraventions in 1993. Rather than see diuron go the same way as the triazines, the manufacturers, Rhône-Poulenc, produced new label recommendations for its use on hard surfaces. The company’s hope is that these new instructions will eliminate the contamination of water or reduce it to a level the authorities will find acceptable(1).
    The key elements of the new recommendations are to use minimum recommended application rates, to avoid runoff, and not to apply over drains, in drainage channels gullies and similar structures. The label changes have been approved by the Pesticides Safety Directorate (PSD) of MAFF, but they are not obligatory, meaning that some products may not carry the new recommendations. The presence of diuron products on the market which allow ‘old’ use patterns may confuse users.
    Industry clearly hopes that the label changes will reduce water contamination, but the PSD is not prepared to comment on the value of label recommendations in preventing contamination. According to PSD, the label change is entirely an industry initiative, in no way prompted by the authorities(2). It will be interesting to see whether they reduce water contamination, and if not, whether the authorities will take action against diuron.

1. Rhône-Poulenc, New diuron recommendations, 8/8/94.                                               
2. Pers. comm. PSD, Ministry of Agriculture 26/8/94. 

[This article first appeared in Pesticides News No. 25, September 1994, page 19]