Fighting a costly fungal foe

Despite experiencing seasons not typically conducive to wheat powdery mildew, WA grain grower Alex Pearce is among a groundswell of growers now battling this problematic disease. Mr. Pearce and wife Cherie farm 4,400 hectares in a wheat and lupine rotation near Minganoo. Over the past three years, they have seen wheat powdery mildew become a serious annual problem.

So it wasn't a huge issue. We were always fungiciding as we went, but 2013, it became more prevalent. Disease in 2015 totally went against the rule book as it did in 2014. We didn't have the moist conditions, we didn't have the large biomass, we didn't have high humidity, we were low humidity, we were dry, low biomass, and it was very, very hot. And the powdery mildew just kept growing even after initial fungicides. So it's starting to become an issue. And that's why the only thing we can think of is maybe a variety change and a different source of fungicide.

Mr. Pearce is looking to change his fungicide program and introduce new wheat varieties beyond wild ketchum in a bid to improve control of wheat powdery mildew, say 2015.

We've stepped it up to probably an $18 a hectare fungicide regime now, and that seems to be the minimum cost we're going to have each year. As far as yield loss goes, we're not too certain on it. And I think that's where local grower groups with continuous trial work, we need to do that every single year. So farmers and in different spots around the area, just so we can ascertain what actual yield losses are occurring in different climates, different soil types. So as we spend the money on fungicides, we actually know what sort of return on investment we're getting.

Research funded by the Grains Research and Development Corporation has shown powdery mildew infection early in the season can significantly reduce wheat yields by up to 25%. By reducing photosynthetic leaf area, causing abortion of young tillers and stunting plant growth. GRDC and Curtin University are investing $100 million over a five year period in the WA based Centre for Crop and Disease Management based at the university, to tackle diseases such as wheat powdery mildew. Director of the Centre for Crop and Disease Management, Professor Mark Gibbard said researchers had seen a change in wheat powdery mildew's pathogenicity.

We know a lot about barley powdery mildew and we know that wheat powdery mildew is very closely related, but the emergence of the pathogen this year took us by surprise. So organisations like DAFA and also the CCDM have been able to respond to that very, very quickly. And dafwa, for example, has done a whole heap of really valuable work directly with industry and with growers. And we've been able to go out and look very carefully at the pathogen and try and understand whether or not its emergence and prevalence this year has been a result of a change in fung resistance, for example, which is something that we've been able to rule out within the first year, at least with respect to the resistance methods or mechanisms that we know about at this stage. So we've certainly seen a change in its pathogenicity, we've seen it move to a much higher incidence on Mace, which has in the past been putatively resistant wheat variety, and we'll be watching it very closely into 2016.

Professor Gibbard said the CCDM was taking a multifaceted approach to tackling fungal diseases like wheat powdery mildew that would benefit growers throughout Australia.

The GRDC funded research at the CCDM benefits Australian grain growers in four main ways. First of all, we have an effort focused on agronomic practice, which works directly with industry to help to develop better ways of dealing with fungal infections by either reducing their incidence or by developing better control mechanisms in the field. The second area focuses directly on the fungus and the plant interaction, and through that we're generating the methodologies that allow breeding companies to develop better varieties that have higher levels of resistance for insects. Industry. The third way is looking at fungicide resistance and also so we can map the development of fungicide resistance across the country, and we can also then look at new fungicides and new potential active compounds and their role and their potential use with industry as well. So they're field trials that are largely done in conjunction with industry and industry groups. The final way that we work is looking at bioinformatics and that allows us to go back and mine data sets from the past, but also to mine future data sets as well to generate better outcomes from existing research for growers.