OP dropped in line with companys new policies
By Andrew Blake
DIMETHOATE, a relatively cheap and widely-used organophosphorus (OP) insecticide, has been dropped for aphid and thrips control by a leading farming company.
Velcourt says the move follows trials pinpointing equally effective chemicals which are safer to the environment and beneficial insects.
It is part of a longer term aim to ban all OP usage on crops on the 26,000ha (65,000 acres) the firm farms. Only for wheat bulb fly control, where there are no current alternatives, will dimethoate continue to be used.
"Its not a very nice chemical to work with," says director Roger Waite. Game Conservancy work confirms its adverse impact on wildlife, he adds. "If you look to the COSH* assessment it is difficult to justify using an OP if there is something to replace it."
Cypermethrin is a good substitute against aphids, and cypermethrin/pirimicarb is even better, though more expensive, says Mr Waite. For thrips Hallmark (lambda-cyhalothrin) is probably best, he adds.
Tefluthrin (Force) seed treatment, successfully used against wheat bulb fly in France for several years, may soon allow dimethoate to be dispensed with altogether on cereals, he adds. Zeneca confirms it hopes to have a UK product available for next autumn.
Mr Waite is adamant that no specific incident triggered Velcourts decision. Provided operators stick to label instructions the insecticide remains safe to use, he stresses. "There is no indication that the label information is inadequate."
Neither has end-user comment had any direct impact, he maintains, though expected supermarket pressures were considered.
Crop consultant John Tunaley of Suffolk-based Independent Agronomy believes Velcourts action reflects growing unease surrounding use of OPs highlighted by problems with sheep dips.
"We took a similar line two years ago on dimethoate." His main concern is for operator safety – less so the environment. Booker Farming maintains that, apart from rare and isolated requirements where no practical alternative was available but where proper permitted applications could safely be made to crops, it has not used OP sprays on cereals for several years.
CWS is already well down the route of avoiding OPs, despite the extra cost, according to spokesman John Bewley. "Our policy for some years has been to pick chemicals which do the least environmental damage."
• Dimethoate is under review by the Pesticides Safety Directorate, a process likely to be overtaken soon by an EU review, says BASFs Tony Grayburn.
UK usage rose from an estimated 106t in 1992 to 225t in 1995, partly due to orange blossom midge attacks. With fewer aphids about this autumn, sales have slipped to 74t, he says.
• OP insecticide dimethoate banned for aphid and thrip control by Velcourt.
• Prompted by environment and operator safety fears.
• Effective alternatives.
• Will cost more.
• Welcomed by Game Conservancy.