12 September 1997

Key weapon approved in fight against blackgrass

Tea-bag technology giving cereal growers a fresh weapon against blackgrass and other key weeds will be on the market this autumn. Andrew Blake reports

DU PONTS Lexus Class, containing the new sulfonylurea flupyrsulfuron-methyl and a novel broad-leaved weed-killer carfentrazone-ethyl (Arable Aug 29), has received full UK approval – ahead of all other EU countries.

Applied at a recommended rate of only 60g/ha it is supplied in small water-soluble 1ha bags and offers the same low dose chemistry and convenience as the firms spring herbicide Ally (metsulfuron-methyl), says the firms Martyn Rogers.

Price has not yet been set. "It will be competitive with current standards in the market-place," Mr Rogers comments.

The active ingredients provide contact and residual control of a wide range of grass and broad-leaved weeds, but not wild oats. Good results can be expected on increasingly troublesome cranesbill. Large pansies are potential escapees, but the need to over-spray in the spring against cleavers should be reduced.

Spray timing is flexible, from the one-leaf stage of the crop to mid-tillering of blackgrass.

Lexus Class may be used on winter crops of wheat, oats, rye and triticale but not barley and offers more consistent and reliable blackgrass control than isoproturon (ipu), says DuPont.

The new herbicide is compatible with aphicides, trifluralin (as in Treflan) and pendimethalin (Stomp), but should not be mixed with ipu, Mr Rogers warns. "It is clearly antagonistic." The addition of just 1 litre/ha of ipu, perhaps with a view to boosting meadow grass kill, is enough to trim blackgrass control from 95% to 85%.

Dont cut rate

Dose justification data suggests there is little room for reducing the recommended application rate, he adds. "If you are tank-mixing you could go to 50g/ha, but there is a very steep fall off in weed control at 40g."

Trials on a densely infested non-resistant blackgrass site in Cambs show Lexus Class matching Hawk (clodinafop + trifluralin) plus oil in giving best control (95%) of the weed, says technical manager, Steve Cranwell. By contrast a pendimethalin/ipu mix saw 20% of plants to survive.

On a mildly resistant site at ADAS Boxworth the picture was equally encouraging. "Even on its own Lexus gave an acceptable level of control – 98%," says Mr Cranwell.

Latest blackgrass beater Lexus gave equal best control of the pernicious weed in this Cambs trial and is available this autumn, says DuPonts Martyn Rogers.

LEXUS CLASS

&#8226 Low dose herbicide for grass/blws in cereals.

&#8226 More reliable than isoproturon.

&#8226 Good environmental profile.

&#8226 Anti-resistance building block.