SA croppers are being urged to adopt a multi-faceted strategy to reduce the threat of septoria in this season's crops, and slow the disease's growing fungicide resistance.
Subscribe now for unlimited access to all our agricultural news
across the nation
or signup to continue reading
Speakers at a GRDC septoria workshop in Riverton last week agreed that while developing a fungicide program to deal with a range of diseases is important, other factors including sowing time, crop rotations and identification techniques are pivotal in combating the disease.
With strobilurins not working on septoria in Europe, resistance found to succinate dehydrogenase inhibitors last year and azoles not as effective as they once were, FAR Australia managing director Nick Poole said that sowing trends could leave the door wide open for the disease.
"We've got this thrust to early sowing and I think that diseases like Septoria, coming in, will thrive on more early sowing," he said.
Mr Poole said septoria's long latent period – when the crop is incubated but the disease is undetecable – of 14 to 42 days was a major problem for farmers because the crop appeared clean.
Difficulty of detection made stubble management imperative and Mr Poole said trials in 2014 showed grazing of early-sown wheats could be as effective as early season fungicides. With little resistance to septoria in wheat varieties, Mr Poole suggested carefully planning when to sow certain varieties.
"If you've got something that's very susceptible, try and avoid it in those really early sowing niches," he said.
The importance of inspecting crops at growth stages 30-32, 37-39 and 59, especially after long periods of humidity or frequent five millimetre rainfall events, was another management technique suggested to support fungicide use.
Mr Poole said SDHI fungicides reduced septoria spore germination, but were at moderate to high risk of resistance development, particularly if used alone.
"Mixing with the azoles is an essential for curative activity," he said.
The workshop revealed that Amisar Xtra (azoxystrobin and cyproconazole), Radial (azoxystrobin and epoxiconazole) and Opera (pyraclostrobin and epoxiconazole) did not have septoria control on the label but were known to be effective, from extensive trials, on a range of foliar diseases.
NSW Department of Primary Industries plant pathology technical officer Merrin Spackman suggested rotating fungicides and using mixtures to avoid encouraging fungicidal resistance.
"Although the field efficacy for a number of products remains good, continued reliance on triazoles presents a selective environment favourable for the emergence and spread of resistance."
