7 July 1995

Resistance can be beaten

By Charles Abel

HERBICIDE-RESISTANT grass weeds can be brought under control, provided the right integrated approach is adopted, says a leading herbicide manufacturer.

"We have achieved a 100% cure on sites where we have had bad resistance. It is possible to get on top," says Andy Piggott, herbicides product manager at Ciba.

Appropriate strategy

No one product provides a complete solution, he stresses. But if an appropriate strategy using cultivations, rotation and herbicides is developed for each field a cure is possible.

The companys new autumn herbicide Hawk has a valuable role to play both where resistance is a worry and in more general situations, he continues.

"Weve shown that with integrated management Hawk provides better control of resistant blackgrass than anything else available. But it has to be part of an integrated programme and there is no one blueprint. It has to be developed for each situation."

Resistance is more widespread and more significant than many growers realise, he adds. "It is greatly underestimated on farms. All the evidence were collecting points towards it being far more significant than expected. Growers in Essex, Oxon and Lincs have faced high populations of difficult to control weeds this spring. We believe resistance is the problem."

Together with variable blackgrass control and a ruling on the use of isoproturon expected soon, Hawks arrival is timely, reckons Mr Piggott. "The combination of contact and residual action provides more consistent control of blackgrass, both between seasons and sites."

The active ingredients are the contact herbicide clodinafop (as in Topik) plus the established residual trifluralin (Treflan).

To optimise control, timing must be spot on – after crop emergence and when blackgrass has three leaves. That may be a week to 10 days later than conventional autumn treatments, but ensures clodinafops contact action "effectively returns the field to zero", explains Mr Piggott. Trifluralin then provides ongoing residual control.

Correct timing is rewarded with "a better result than ipu," says Mr Piggott. Marketing as a twin-pack will be limited this autumn. Pricing will be "competitive", especially when growers consider the need for return sprays following other treatments, he points out.

&#8226 Hot on the heels of Hawk is a clodinafop/diflufenican mix, developed with Rhone-Poulenc. It controls grass and broad-leaved weeds, with approval for low rate ipu tank mixes, explains Mr Piggott. Availability will be through four main distributors.

There is no single blueprint for countering herbicide resistance, says Cibas Andy Piggott. He believes the problem is more widespread than many growers realise, but integrated management should retain control.