28 July 1995

Industry experts welcome herbicide recommendations

By Robert Harris

INDUSTRY experts have welcomed the Advisory Committee on Pesticides recommendations arising from its review of cereal herbicide isoproturon after concerns over drinking water standards.

The expected IPU limit of 1.5kg/ha has been deferred at least until results of research into reduced rates are available. Instead, applications will be restricted to 2.5kg/ha, the maximum label rate.

The loophole which lets growers apply more than this by using a sequence of different brands has been stopped. Pre-emergence use has also been banned. But the broad feeling is its business as usual – for now.

Ag-chem distributor Profarma believes common sense has prevailed. "Distributors can continue to give sound advice to farmers on grass weed control in cereals without any major hindrance," says general manager Paul Singleton. "But there is plenty of room for future amendments. Further restrictions are likely."

He welcomes the abolition of product sequences. "The loophole which allowed the maximum dose to be exceeded has quite rightly been removed. In practice this tactic was almost never good advice."

The Association of Independent Crop Consultants chairman, Simon Draper, agrees. "Although some results show double rates can control resistant blackgrass, environmentally there is no real defence for it."

He sees few problems with the review, including the pre-emergence ban. "We only used pre-emergence IPU in exceptional circumstances, for example on a late-drilled crop with a wet forecast, so the ban wont greatly affect our use of IPU at the moment."

If a 1.5kg/ha rate is eventually introduced, he will apply a programme similar to one he uses to control IPU-resistant blackgrass. "Weve started using Avadex pre-emergence and followed with IPU at 1.25-1.5kg/ha, or the same rate of IPU followed by a specific blackgrass killer."

Cost penalty

But there will be a cost penalty. "Four litres of IPU costs about £12/ha. Avadex alone is about £20/ha," he says.

Stephen Moss, research scientist at IACR Rothamsted and secretary of the Weed Resistance Action Group, welcomes the reviews recognition of the need for further research before a 1.5kg/ha limit is considered.

Although there is little problem with this rate on normal blackgrass, it is unlikely to be enough to control the increasing number of sites with appreciable levels of resistance. "You normally need a full rate of IPU before adding other chemicals. There is a need for more research. Clearly the ACP allowed for this."