New WA research targets common oat disease of Septoria leaf blotch

Problematic western region oat disease being tackled in new project

Weeds, Pests, Diseases
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Managing Septoria leaf blotch is in the spotlight as more WA growers add oats to rotation.

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Septoria leaf blotch commonly causes yield losses of about 10 per cent in high-rainfall areas. PHOTO GRDC

Septoria leaf blotch commonly causes yield losses of about 10 per cent in high-rainfall areas. PHOTO GRDC

Interest in growing oats has increased in Western Australia in recent years and there is now a greater research focus on how to manage diseases - including Septoria leaf blotch - the State's most common oat disease.

Initial trial results have highlighted the need to match fungicide programs to infection levels of this stubble-borne disease, which in high-rainfall areas commonly causes yield losses of about 10 per cent and staining in some varieties such as Bannister (PBR).

Variety planning at harvest

Grain growers currently harvesting crops may be considering Septoria resistance levels and management as they look ahead to next year and consider which oat varieties to grow in 2020.

The GRDC has increased its investment in research that aims to provide WA growers with best practice management guidelines to reduce losses in yield and grain quality caused by Septoria and other oat diseases.

WA Department of Primary Industries and Regional Development (DPIRD) plant pathologist, Geoff Thomas, says oat diseases are now being specifically addressed as part of the broader GRDC-invested project 'Integrated disease management (IDM) in western region grain crops'.

"This project aims to deliver growers new information on the impact and causes of major oat diseases and guidelines on how to manage them," Mr Thomas says.

Rolling out the project

Mr Thomas says the first year of dedicated oat disease trials under the IDM project have been located at Highbury, Northam and Wongan Hills.

"Dry seasonal conditions and low disease levels mean that yield impacts and fungicide responses of Septoria have been limited in 2019," he says.

With previous GRDC investment, farm consultancy ConsultAg investigated Septoria in oats as part of a 2014 project initiated by the Kwinana West Regional Cropping Solutions Network, and again in 2017 and 2018 as part of a DPIRD oat agronomy and industry development project.

In 2019, ConsultAg has conducted further trials at Highbury and Lake Grace as part of the DPIRD IDM project - to further the understanding of potential management tactics for Septoria.

"Our trials aim to determine the best fungicide and timing strategy to reduce staining in Bannister (PBR) oat grains, and to evaluate the economic returns from foliar fungicide application on oats," ConsultAg consultant Trent Butcher says.

When to consider a fungicide

To date, this trial series has shown that foliar fungicide applications can reduce the severity of Septoria in Bannister (PBR) oats and result in a profitable yield response when spring rain is sufficient to achieve high yields.

"It has also demonstrated that fungicide application can reduce the amount of grain staining but cannot provide complete control," Mr Butcher says.

"Grain staining therefore is likely to remain a potential risk, but fungicide may increase the chances of growers meeting delivery standards."

Mr Butcher says the trials had shown fungicide applications during head emergence were most effective in reducing grain staining. But this was not the most economic approach, as these later timed fungicide applications did not maximise yield responses where the disease was present at damaging levels on leaves.

"The trials show that, in order to both maximise yield gains and reduce staining, it is best to apply fungicide when Septoria is present at the full flag leaf to mid-booting stage," he says.

"Growers in medium to high-yielding areas should consider a two-spray strategy if growing Bannister (PBR), or other varieties susceptible to Septoria, on oat stubble."

Mr Butcher says the trials had demonstrated the importance of carefully inspecting oat crop plants for disease, including at the bottom of the plant canopy, to inform fungicide decisions, as the disease could develop rapidly during warmer temperatures above 20°C.

More information about Septoria is available in the GRDC's Western Oats GrowNotes™ publication and on the DPIRD website.

GRDC Research Codes: DAW1907-001RTX, DAW00227

More information: Geoff Thomas, DPIRD, 08 9368 3262, 0428 947 287, geoff.j.thomas@dpird.wa.gov.au; Trent Butcher, ConsultAg, 0417 137 211, tb@consultag.com.au

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