Barley net blotch warning

The West Australian

Growers are urged to carefully plan fungicide management strategies for net blotch in barley crops this season after the discovery of a population of the disease resistant to commonly-used fungicides.

Curtin University researchers have discovered a barley net-type net blotch population from WA resistant to the triazole fungicide tebuconazole, as well as some other types of triazole fungicides.

Net blotch - a disease that can cause substantial yield and quality losses in barley - reached damaging levels in WA barley crops last year, especially in high rainfall, southern areas of the State.

The discovery of the resistant population of NTNB, also known as net form of net blotch, was made at the Centre for Crop and Disease Management.

CCDM fungicide resistance group program leader Fran Lopez-Ruiz said to minimise the risk of NTNB in 2015, growers should use a range of fungicide and crop management strategies.

"Management strategies include reducing the risk of disease carry-over by avoiding sowing barley on barley stubble, and avoiding barley varieties susceptible to NTNB in disease-prone environments," he said.

"Growers need to avoid spraying barley crops with straight tebuconazole products, which are registered to control powdery mildew and scald, because there is a high risk that this will encourage the development of NTNB resistant populations.

"They should instead ensure that they use alternative fungicides mixes that contain a quinone outside inhibitor, as NTNB is unlikely to develop significant resistance to Qol."

Department of Agriculture and Food research officer Andrea Hills warned growers to assess their crop's disease risk and to plan accordingly.

Ms Hills said another type of blotch, spot type net blotch, which has been prominent in recent years, would pose a risk to barley crops - particularly those sowing barley on barley.

"Early sown crops are likely to be exposed to high STNB disease pressure as fungal spores are initially released from barley stubbles after rain and when temperatures are between 15 and 25 degrees centigrade," she said.

With more than 85 per cent of the State's barley sown to varieties that are susceptible to STNB, Ms Hills urged growers to avoid high risk crop rotations and incorporate fungicide treatments into their budgets.

"Heavy barley stubbles from 2013 will still be releasing STNB spores that can infect crops this season," she said.

"While there are range of effective foliar fungicides, basic agronomic measures, such as ensuring soil potassium levels are above 50 parts per million, can also assist crops.

"An application of fungicide at stem extension has been shown to be most effective, with a follow-up spray three to four weeks later in medium to high rainfall areas.

"Burning infected barley stubbles could be used as a last resort to reduce risk of STNB."

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