Fungicide control of powdery mildew, net blotch

THE right fungicide treatment (seed dressing or mixed with fertiliser in furrow) could save much of WA's barley crop from the yield losses now caused by powdery mildew. A spray-based fungicide approach could also safeguard against spot form net blotch.

In high production situations, in-furrow fungicides can increase barley yields by giving longer protection than seed dressings against powdery mildew.

These were some of the findings from an Agriculture Western Australia project, supported by growers and the Federal Government through the GRDC, investigating ways of controlling two of WA's most difficult barley diseases ~ powdery mildew and spot form net blotch.

Principal investigator Kith Jayasena reported that the experiments at Katanning have shown similar benefits from using seed dressings or in-furrow treatments for powdery mildew on Stirling. However, Gairdner did not develop sufficient disease to warrant powdery mildew control in that environment.

He said that, under more favourable disease conditions, the impact of powdery mildew can extend beyond the eight-week period, after which seed dressings lose their efficacy.

"Experiments carried out by IAMA agronomist Quenten Knight for the last two seasons demonstrated that significant yield increase could be gained from the use of in-furrow fungicides over the standard practice of a fungicide seed dressing. The extended protection from in-furrow fungicides can be from eight to 16 weeks. Early treatment of Gairdner was not so critical as it was less susceptible to powdery mildew."

If seed treatments are omitted, protection against powdery mildew with fungicide spray can also be cost-effective. Dr Jayasena reported that results on Stirling at Gibson in the south-east region showed a fungicide spray could reduce the severity of mildew and increase yield by 13 per cent, equating to 0.5 t/ha in this case.

Proliferation of net blotch

The adoption of Franklin and the expansion of Gairdner as malting barley in the south coast region have seen the proliferation of spot form net blotch fungal disease.

Seed treatments and in-furrow fungicide treatments are ineffective against the disease. Research with foliar fungicide sprays found this disease could be effectively controlled through a single application of propiconazole at 250-500 mL/ha, significantly improving yield and in some cases quality.

Program 2.6.3 Contact: Dr Kith Jayasena 08 9892 8477 email kjayasena@agric.wa.gov.au

Growers seeking specific chemical recommendations Gre urged to seek advice from the Department or from farm advisers - Ed.

Region North, South, West