2 March 2001

Seeing off rhyncho

MIXING or alternating triazole fungicides with other fungicide groups will increase the effectiveness of rhynchosporium control in barley, according to HGCA-funded research at the Queens University of Belfast, conducted in partnership with ADAS.

Growing resistance of rhynchosporium to triazoles means fungicides from this group should not be used alone and repeatedly on the same crop, warns project leader Dr Louise Cooke.

She is studying the effectiveness of 12 treatments based on Opus (epoxiconazole), in sequence or mixed with Unix (cyprodinil), Corbel (fenpropimorph) or Amistar (azoxystrobin) in a two-spray programme.

In six field trials from 1998-2000 in Northern Ireland and south-west England, Opus alone gave relatively poor disease control but a better yield than untreated control plots.

Applying one of three different fungicide partners either singly, or in combination, significantly increased rhyncho control.

A mix of Opus and Unix at both T1 and T2 cut infection to 9% of the leaf area, compared with 16% for the two-spray programme of Opus alone. An Opus/Amistar mix had a similar effect, while Opus/Corbel reduced disease level to 10% of the leaf area.

"Even with reduced winter cropping this year it is likely that there will still be a high risk of rhynchosporium because of the wet conditions," says Dr Cooke. "To achieve optimum control and reduce the risk of further selection for resistance, use triazole fungicides in mixtures or alternate with partners from other groups."

Further information about the work is available on a new HGCA Topic Sheet (No. 42) – Rhynchosporium control programmes.