Rise in fungicide resistance causing concern in WA

Grain Central, April 20, 2020

DEVELOPING populations of fungicide resistant diseases in Western Australia is causing concern and while it is not yet time to panic, it is time for the industry to act, according to the WA Department of Primary Industries and Regional Development’s (DPIRD) Geoff Thomas.

Speaking at the Bayer Connect annual update in Perth, Mr Thomas said in the early 90s in the case of controlling septoria tritici in wheat, it was viewed that a fungicide like propiconazole, which was far more expensive at that time, was rarely used because of comparatively lower yields, uncertain economic returns and availability of varieties with some resistance to the disease.

It was suggested that fungicide sprays may offer a cost-effective means of reducing losses caused by septoria tritici and septoria nodorum in southern WA when yield potentials and disease levels were high.

Whilst appreciating the higher yields now possible and lower costs of some chemicals today, Mr Thomas said fungicides, still including propiconazole, were now widely and routinely used.

They are considered a cost-effective means of reducing losses from diseases when they are yield limiting across a wide range of environments, so much so that this is now threatening their efficacy.

“In 25 years, we have gone from the opinion that fungicides might give us an economic response, to them being at the top of the tree in terms of how we think about disease management,’’ he said.

“Fungicides are now our go-to step in terms of managing fungal diseases.’’

WA Department of Primary Industries and Regional Development’s (DPIRD) Geoff Thomas (centre), with the Bayer’s Head of Market Development Australia and New Zealand, Rick Horbury, and Farmanco consultant David Cameron.

Mr Thomas said grain crop diseases resistant to fungicides in WA included powdery mildew in barley, which had been known for more than 10 years, blackleg in canola and, more recently in the state’s South Coast region, net blotches in barley, which were providing increased concern.

In other parts of the country, powdery mildew resistance in wheat and net form net blotch resistance to SDHI (succinate dehydrogenase inhibitor) fungicides in South Australian barley also are raising some alarm.

Mr Thomas said to help effectively manage resistance, the focus was on halting the repeated use of the same mode of action fungicides, thereby preventing disease selection pressure.

He said in barley, scenarios contributing to high disease pressure in recent years could have included most varieties being susceptible to spot form net blotch, a near doubling of production and a significant portion of that area being sown into barley stubble.

“We’re setting up situations that are promoting high levels of disease, which then puts maximum pressure on our fungicides.’’

Mr Thomas said the resistance development required careful consideration with growers about what they were doing in their paddocks, as well as how the industry responded to the issue.

“The message is the same as for herbicides. Fungicides are a finite resource, so we have got to try and hang onto them for as long as we can,” he said

“Try to reduce the reliance on fungicides as the sole disease management tool. If a system ties you to fungicide, can you alter that system? Can we use the fungicide as the cream on the cake rather than the pillar that the disease management is resting on? Can we stick a non-barley in that barley rotation?

“We do have options. There is a wider choice of fungicide groups and there are different application technologies, including seed, fertiliser and foliar. We have different ways of putting out different modes of action before seeding our crop. It gives us many ways to achieve our goal.’’

Mr Thomas said the industry needed to maximise how fungicides were used, and could ask a number of questions when considering applications.

“Do you need to apply that fungicide? Is that fungicide giving you a positive return on investment? Are you maximising the chance of efficacy with that fungicide by using the appropriate adjuvants or other products?’’

He said the best fungicide application rate to help minimise disease selection pressure was the lowest effective, economically feasible rate, however this also needed to be considered in conjunction with other fungicide treatments that may already have occurred.

“It’s about using the products for what they should be used for. Just because the sprayer was going over the paddock doesn’t make it right to put a fungicide on,” he said.

“We have to use the products in the appropriate way and maximise the effectiveness of their use to get our return on investment and also to protect them. And when there are SDHI products doing a great job on net blotches, we don’t want to just recognise how well that mode of action works and then throw them out the window.’’

He said fungicide resistance management equalled good disease management that started with variety selection followed by integrated management and then fungicide.

“Many of our systems, however, are flipped over the other way now and we are teetering on the capacity of our fungicide to do the job.’’

Fungicide rotation

Corrigin Nutrien agent from Sellars Ag Services, Angus Sellars, said he recognised rotating fungicide chemistry was becoming critical for growers.

“In our region, where we have some barley-on-barley, instead of just using propiconazole, we are going to have to start breaking that up. We have started to do that, but I think we have got a few more tools in the shed with Bayer now that we can really utilise,’’ he said.

Ella Kelly, who works in research, development and extension with David Grays Aglink, said the research was showing the industry could no longer misuse fungicides because resistance was now such an issue.

“It’s about driving the message to growers to use our chemistry to the best of its ability and not take advantage of it, so it has longevity in the market,’’ Ms Kelly said.

Mr Thomas said to further assist the industry, the recently established, GRDC-funded Australian Fungicide Resistance Extension Network (AFREN) would continue to generate information to help growers and advisers understand the status, risks and management of fungicide resistance in Australian grain crops, while it also would deliver a management guide and workshops in the future.

Source: Bayer




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