Septoria vigilance urged despite dry conditions

DESPITE the dry conditions in many parts of eastern Australia, growers have been urged to remain vigilant for cereal crop diseases including septoria tritici blotch (STB) in relevant and susceptible areas – and particularly if spring rainfall is received.

STB has become an increasingly important stubble-borne foliar disease of wheat, especially in higher rainfall zones of southern Australia.

Nick Poole, Managing Director of the Foundation for Arable Research (FAR) Australia, said STB was one of seven most problematic diseases encountered in southern Victoria over the past eight years.

“It’s a disease that’s reasonably endemic in wheat crops in Tasmania and southern Victoria, and last year we saw the spread of the disease into different parts of South Australia, as well as up into Southern New South Wales,’’ Nick said.

He said with the dry conditions in many areas this season, it could be considered that it should not be a problem, however this was not necessarily the case.

“We saw septoria tritici in some of the earliest wheat crops in early May.’’

“First lesions were showing up in crops in mid-June and now you can find the disease on lower leaves of some of our susceptible varieties.’’

As a result, Nick said it was still very worthwhile to be looking out for STB, especially through southern high rainfall zones.

“It’s easy to identify – with the black fruiting bodies on the leaf lesions.’’

He said disease control was important considering the cropping outlook was actually quite good in some southern areas, which traditionally can face water-logging issues most winters.

STB earlier became more difficult to control in cereals when two-gene fungicide resistance was discovered, indicating resistance to some of the common triazole fungicides used. 

However, the arrival in recent seasons of the dual mode of action, broad spectrum foliar fungicide, Radial® from Adama, has helped growers to improve their management of the disease.

Wheat leaves infected with Septoria tritici blotch. The fungus causes pale grey to dark brown blotches on the leaves, with a typical black fruiting bodies (pycnidia) within the blotches.
Septoria tritici blotch can cause complete death of leaves and significantly reduce yield and grain quality.

The success of Radial against STB in wheat and a wide range of other diseases in wheat and barley is due to the fact it includes the two leading active ingredients for cereal diseases, azoxystrobin and epoxiconazole. Unlike similar products, it is also an EC formulation with micro emulsion properties, with the active ingredients fully dissolved and readily available for crop uptake.

“The dual mode of action provides extended systemic control. It provides both protectant and curative activity of all key foliar diseases in wheat and barley,’’ said Dror Dagan, Head of Portfolio at Adama.

He said Radial targeted infections from the time of spore germination on leaf surfaces, through to development within leaves. Hence, growers applying the fungicide as a preventative treatment prior to spore germination would achieve the maximum return on investment.

Decisions about when to spray Radial this season would depend on a range of factors, including:

  • Disease pressure
  • Visual symptoms
  • Earlier seed dressing/in-furrow applications
  • Crop growth stage, ensuring protection of the “yield-producing’’ leaves
  • Maximising yield potentials.

Early-sown crops and crops sown into wheat stubbles are most at risk of infection.

Trials have indicated Radial performs very well at a rate range of 420-840mL/ha, applied between stem elongation and complete ear emergence.

For further information about Radial foliar fungicide, growers, advisers and agronomists can contact their local Adama representative.

(This article appeared in the October 2018 Edition of Rural Business Magazine)