Canola sclerotinia update

  • Avon Valley
  • Northam
  • South Stirlings
Sclerotinia ground infection
Sclerotinia ground infection. Photo courtesy of: Ravjit Khangura (DPIRD)

Andrew Reynolds (Elders) has tweeted about seeing sclerotinia ground infections and leaf infections in the advanced/wetter areas of some canola paddocks in the Avon Valley.

Sclerotinia apothecia
Sclerotinia apothecia. Photo courtesy of: Bec Swift (DPIRD)

Crop protection officer Bec Swift (DPIRD) has found sclerotinia apothecia in a canola crop near Northam.

Farmer Reece Curwen has found sclerotinia leaf lesions in his flowering GT53 canola at South Stirlings. There was a nearby canola paddock infected with sclerotinia last year.

Plant pathologist Ravjit Khangura (DPIRD) says that the fewer sclerotinia reports received this season are due to less than ideal seasonal conditions for sclerotinia spore release and disease development in many canola growing regions across the grainbelt.

DPIRD research over the past few years has shown that as a rule of thumb more than 40mm of rainfall and more than 75% relative humidity (RH) in the three weeks before and after commencement of flowering are most conducive for the damaging levels of sclerotinia to occur in crops.

Canola bloom stages are also quite variable in different regions.

Some of the key risk factors of sclerotinia stem rot include; history of sclerotinia in the current canola and surrounding paddocks and conducive weather conditions around flowering.

Ravjit urges growers to check their rain gauge or weather data from the nearest department weather stations and the growth stage of their canola.

Several fungicide products that are made up of the actives prothioconazole + tebuconazole, procymidone, iprodione and more recently prothioconazole + bixafen are registered for the control of sclerotinia in canola. Fungicides need to be applied as per product label. More information can be found at the department’s Registered foliar fungicides for canola in Western Australia.

Based on the research conducted by DPIRD over the last few years, growers who have a history of sclerotinia infection in their current canola paddock need to consider;

  • Applying a single foliar application at 30-50% bloom. Provided conditions are favourable for infection before and during flowering.
  • Carrying out two spray applications is ideal when an extended season is experienced, but this is unlikely to be the case this season.
  • Carrying out late spray applications (up to 60% flowering and beyond) is generally not expected to be economical this season, particularly in the Southern region.
  • If growers notice ground infections they can apply a foliar fungicide immediately or wait until 20% bloom to prevent further new infections.

Before applying fungicides growers also need to consider the crop yield potential, costs of fungicide and application and canola price.

Further information can be found at the department’s Managing sclerotinia stem rot in canola page and GRDC’s Managing sclerotinia in canola YouTube video.

For more information contact Ravjit Khangura, Research Officer, South Perth on +61 (0)8 9368 3374.