Don't get complacent about disease in dry

Don't get complacent about disease in the dry

Cropping
Grant Hollaway, Agriculture Victoria plant pathologist, says farmers need to remain vigilant against the threat of crop disease this year.

Grant Hollaway, Agriculture Victoria plant pathologist, says farmers need to remain vigilant against the threat of crop disease this year.

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There may have been a low foliar disease burden last year, but farmers need to remain vigilant this season, according to a disease expert.

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IT MAY have been a dry start to 2019 but December rain has provided a green bridge of weeds and crop volunteers to provide a host for disease inoculum to build up on, so farmers should not be complacent about potential disease risk for the upcoming winter crop.

That was the message from Agriculture Victoria plant pathologist Grant Hollaway at the Grains Research and Development Corporation (GRDC) update in Bendigo earlier in the month.

Dr Hollaway said the lessons of 2016 showed farmers should not underestimate the disease threat based on a dry summer beforehand.

"In 2016 we'd had a very dry 2015 in Victoria followed by a dry summer but then the season came in wet and there were issues with fungal disease," he said.

He added that root-borne diseases were worse in dry season, saying last year, which was drier than average for much of the Victorian cropping belt, saw yield losses of up to 50 per cent in isolated cases from crown rot.

He said the early summer rain this year may have provided a sufficient green bridge for rust inoculum to survive, in spite of the searing temperatures and the lack of rain from January onwards.

"In the absence of proactive control, you can lose up to 20 per cent of yield from these fungal diseases so it pays to be proactive,"Dr Hollaway said.

He said avoiding the use of highly susceptible varieties, combined with identifying paddocks with a higher risk of either foliar or root disease was a critical step in mitigating risk of serious yield loss.

Dr Hollaway said it was important farmers did not overlook the significance of root-borne diseases, in spite of the fact symptoms do not present as dramatically as with rust, which is clearly visible.

"Using testing such as Predicta-B can help in identifying problem paddocks for root diseases," he said.

He said crown rot, a root-borne disease, was now possibly the most economically damaging disease in wheat nationally.

"Yield losses from soilborne diseases can go unrecognised as symptoms are below ground," he said.

However, he said studies had showed annual average yield losses of 7 per cent through Victoria and SA as a result of crown rot.

"Managing disease is going to be important in maximising yields in cereal crops, even if you don't think you are likely to have a heavy disease burden," Dr Hollaway said.

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