WA growers urged to check crops after wet start provides ‘ideal’ conditions for stem rot fungus

Headshot of Shannon Verhagen
Canola in a Scaddan field.
Camera IconCanola in a Scaddan field. Credit: Kalgoorlie Miner

WA canola growers are being urged to assess their crops’ risk of a destructive and “unpredictable” fungal disease capable of axing yields by 20 per cent.

It comes after farmers upped their plantings of the grain this season off the back of a wet start to the season and high prices, leading to a record crop for the State.

But the wet weather has also provided “ideal seasonal conditions” for the first stages of the sclerotinia stem rot cycle to “flourish,” with reports emerging of an “unusual form” in Jerdacuttup.

Department of Primary Industries and Regional Development research scientist Andrea Hills said timing of treatment was “crucial” and growers needed to assess their risk now and decide whether they needed to spray.

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“If growers are going to spray crops with a registered fungicide, it must be applied prior to disease symptoms developing to be effective in reducing stem rot,” she said. “This is usually during the early to mid-flowering period.

“Sclerotinia stem rot can be one of the most variable and unpredictable diseases of canola and the incidence of infection varies between paddocks and between years.

“In cases of severe infection, yield losses can be more than 20 per cent, while in other situations we have good disease control from fungicide applications but no yield benefit.”

She said the SclerotiniaCM decision support tool — which was developed by DPIRD and New South Wales Department of Primary Industries, with co-investment from the Grains Research and Development Corporation — would give them confidence in making the right call.

The app — which is designed for use during the flowering stage — can be tailored paddock by paddock and takes into account the costs, yield benefits, grain prices and seasonal conditions to give growers and agronomists the best and worst case and most likely outcomes, in yield and net return.

“Using the SclerotiniaCM decision support tool to assess their risk can give growers more confidence whether or not to invest in spraying for the disease and the potential impact of an extended wet period,” Ms Hills said.

“There have even been reports from the Jerdacuttup area of basal stem rot which is an unusual form of the disease that can occur before flowering through direct infection of stems.

“Generally the areas of a paddock with the best crop growth, along with those that remain damper for longer or on fine textured soils, are more likely to have infections. After infected petals fall, stem lesions need very high humidity for a number of days to develop.”

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