26 March 1999

Tridemorph curbed

TOUGH new restrictions on the way a widely used mildew fungicide is handled came into force last week.

They follow on-going studies on rats by manufacturer BASF which suggest a theoretical risk of cleft palates in children born to mothers exposed to tridemorph.

BASF registrations manager, Pam Moult, says the latest move stems from the continuous monitoring required by the Pesticides Safety Directorate to ensure approval data packages on older chemicals meet tighter EU standards. There is no field evidence that tridemorph has caused any human health problems, she stresses.

"It has a definite role in anti-resistance strategies, so we hope this is not the end of tridemorph."

All approvals for tridemorph use on crops other than cereals and by aerial application have been revoked. But tridemorph levels which may be found in food are not of concern, says the governments Advisory Committee on Pesticides.

The main constraint for users is that tridemorph, an active ingredient in many products including Calixin, may now be used only through closed transfer systems. "That is the biggest problem," says BASFs Tony Grayburn. "There are only about 200 in the UK."

Application of tridemorph is now also confined to operators protected by closed cabs, and they will have to wear protective gloves when handling contaminated surfaces.

A new maximum individual dose of 375g/ha is unlikely to cause much practical difficulty, as it coincides with the Calixin label recommendation, says Mr Grayburn.

But Unison (fenbuconazole + tridemorph) from pbi Agrochem-icals, is harder hit. Its label dose of 2 litres/ha delivers 450g/ha of tridemorph, so it may no longer be advertised, sold, supplied or used.

Proposals to allow current farm and distributor stocks to be used at 1.6 litres/ha, which the firm believes is the maximum dose used commercially, have been made to PSD.

Sales of straight tridemorph, first sold as Calixin in 1969, have slipped about 100,000ha (250,000 acres). But it is also in many different mixtures.

A spokesman for Du Pont, whose DUK 51, Fusion, Justice, and Option are all affected, says the firm will do everything necessary to implement the approval conditions. &#42