Preliminary results indicate grazing control

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DAFWA researcher Andrea Hills and technical officer Bruce Simmonds observe powdery mildew in ungrazed barley in a trial plot at Gibson, WA.

Crop grazing could help control barley powdery mildew, a disease that accounts for annual losses of $30 million for Western Australia’s barley crops.

Andrea Hills from the Department of Agriculture and Food, WA (DAFWA) is running the study as part of the GRDC’s Barley Agronomy for the Western Region project.

Ms Hills says strains of powdery mildew that are resistant to the triazole group of fungicides recently increased the risk of damage from the disease. So the trial aims to determine whether growers could avoid early fungicide applications by grazing crops.

In trial work at Gibson, WA, more than five per cent of the lower leaves of BaudinA barley were infected with powdery mildew at a height where fungicide is typically sprayed. A roller and lawnmower were then used to simulate the effects of livestock and then the results scored.

Preliminary findings indicate that following the simulated grazing the barley was ‘clean’ of powdery mildew. Ms Hills thinks the reduced levels of the disease could further help growers deal with fungicide resistance.

“Although this is an initial trial, these results show that crop grazing could be a useful tool in early season disease management, with the added bonus of providing feed for livestock,” she says.

“We still need to find out if barley yields are reduced by crop grazing, if disease levels are reduced in spring and if there is any impact on grain quality for malting.”

Information from the study is being shared with researchers undertaking the Grain & Graze 2 program, funded by the GRDC and the Australian Government’s Caring for our Country initiative.

Ms Hills says the research was prompted by grower reports that grazing by sheep and cattle in barley crops had reduced powdery mildew damage.

The study also examined grazing effects on outcomes of using dressed seed. A low-cost fungicide seed dressing to protect the crop from smut was applied to some trial plots, while in other plots a higher-cost dressing to control early mildew and insects was used.

“If grazing is able to reduce disease levels in the early stages of growth, the more expensive seed dressing may be unnecessary,” Ms Hills says.

“This could save growers’ money that could be better spent on the new generation fungicides, which are still effective against barley powdery mildew. Seed dressings containing an insecticide also have longer withholding periods before crop grazing can commence – up to 10 weeks after sowing.”

Ms Hill says BaudinA barley was used in the trials because it is susceptible to powdery mildew.

The plots were seeded on 11 May and a pea-roller was used to simulate the effect of livestock trampling the crops and levelling the furrows. The plots were then mowed for six weeks until the first node appeared on the crops, which is the stage of development recommended to stop grazing to avoid yield losses.

More information: Andrea Hills, 08 9368 3333; www.grdc.com.au/DAW00190

GRDC Project Code DAW00190

Region West, North, South