PestFacts WA

Powdery mildew found in canola

• Cascade

• Munglinup

• Ravensthorpe

• Borden 

Powdery mildew on canola stems. Photos courtesy of: Andrea Hills (DPIRD). 

Plant Pathologist Andrea Hills (DPIRD) has reported that powdery mildew is present in canola crops around Esperance and Ravensthorpe.

Additionally, Technical Officer Daniel Malecki-Lee (DPIRD) recently found powdery mildew in a canola crop at Borden.

Powdery mildew on canola pods. Photo courtesy of: DPIRD. 

Powdery mildew can infect leaves, stems and pods of canola. Commonly seen from mid to late pod-filling, mildew can affect any part of the plant. Patches often appear on stems and pods and resemble talcum powder. These patches enlarge and coalesce to cover the entire stem. There may also be purpling of the stem under areas affected by powdery mildew.  If pods are infected early, they may remain smaller and produce fewer seeds, and the seeds generally are shrivelled and of poor quality. Presence of the disease may not be noticed until swathing or harvest, when white clouds of spores are generated as machines move through the crop.

The disease development is generally favoured by dry conditions with moderate to high humidity (50 to 95%) and moderate temperatures (15 to 25°C). The disease is also favoured by dense canopy, and by high nitrogen fertilisation in canola.

Canola varieties vary only slightly in susceptibility, and variety resistance to this minor disease is not routinely assessed.

Powdery mildew is not considered a serious problem in Australia since the disease tends to occur too late in the season to cause significant yield loss. In northern NSW, this disease occurs regularly in canola and is thought to reduce yield in some seasons, particularly if the infection progresses to pods. The loss of photosynthetic area appears to be the main cause of yield loss but there is limited data available. The pathogen may survive between seasons on volunteer host plants or brassica/lupin weeds as well as old canola/lupin stubble.

Currently no fungicides are registered for the control of powdery mildew in canola or lupin in Australia, but applications to control sclerotinia or blackleg upper canopy infection (UCI) often reduce its incidence and severity.

Growers and consultants are urged to keep reporting with the PestFacts WA Reporter app if they see powdery mildew, as this will help in determining its distribution and formulating control tactics in the future.

For more information contact Plant Pathologists Ciara Beard in Geraldton on +61 8 9956 8504 or Andrea Hills in Esperance on +61 8 9083 1144. 

Article authors: Ciara Beard (DPIRD Geraldton) and Andrea Hills (DPIRD Esperance).