7 November 1997

New guidelines for resistance in grass weeds

UPDATED guidelines for controlling herbicide resistant grass weeds reflect continuing concern about the rise in resistance problems.

"Wild oat resistance has been confirmed since the original guidelines were published in 1993. And more cases of Italian ryegrass have been identified – 25 cases in several counties," says Jim Orson, a member of the Weed Resistance Action Group steering committee.

Blackgrass cases have also climbed, with resistance now confirmed on 750 farms. Although wild oat resistance is rarer, being found on less than 50 farms, it is potentially a bigger problem, he adds.

"Blackgrass is only found on 0.75-1m ha in the UK, wild oats are found everywhere."

New information aims to help growers differentiate between the two types of blackgrass resistance, so the right control strategy is used, says Mr Orson.

Advice on preventing resistance developing in the first place has also been updated.

More detail on cultural control includes the comment that ploughing reduces blackgrass numbers in winter wheat by 63% more than non-inversion tillage.

Field trials also show that by drilling winter wheat three weeks later than usual blackgrass populations can be almost halved, says Mr Orson.

Copies of the guidelines are available free from HGCA, Hamlyn House, Highgate Hill, London N19 5PR.

UPDATED guidelines for controlling herbicide resistant grass weeds reflect continuing concern about the rise in resistance problems.

"Wild oat resistance has been confirmed since the original guidelines were published in 1993. And more cases of Italian ryegrass have been identified – 25 cases in several counties," says Jim Orson, a member of the Weed Resistance Action Group steering committee.

Blackgrass cases have also climbed, with resistance now confirmed on 750 farms. Although wild oat resistance is rarer, being found on less than 50 farms, it is potentially a bigger problem, he adds.

"Blackgrass is only found on 0.75-1m ha in the UK, wild oats are found everywhere."

New information aims to help growers differentiate between the two types of blackgrass resistance, so the right control strategy is used, says Mr Orson.

Advice on preventing resistance developing in the first place has also been updated.

More detail on cultural control includes the comment that ploughing reduces blackgrass numbers in winter wheat by 63% more than non-inversion tillage.

Field trials also show that by drilling winter wheat three weeks later than usual blackgrass populations can be almost halved, says Mr Orson.

Copies of the guidelines are available free from HGCA, Hamlyn House, Highgate Hill, London N19 5PR.