Watch out for Anthracnose

After years of drought, growers are now experiencing perfect conditions for the development of lettuce anthracnose.

Anthracnose is a serious disease of lettuce caused by the fungal pathogen Microdochium panattonianum.

In Southern Australia lettuce anthracnose usually occurs in late autumn, winter and spring months during cool seasons when there is significant rain.

Anthracnose initially causes small water-soaked spots along the midribs of lower leaves. Spots enlarge, turn yellow, and are usually irregular and angular in shape.

In a severe outbreak, anthracnose lesions coalesce and turn leaf tissues brown leading to significant crop losses.

Optimum conditions for disease development are between 5-27°C with 8 hours of leaf wetness. Symptoms appear in 8-17 days.

Crop losses can occur in seedlings nurseries, field crops, even in the coolstore after harvest.

Professor Victor Galea, one of the pioneers in Lettuce Anthracnose research, said:

“We may need to revisit the research that was conducted more than 25 years ago to find out which Anthracnose races we have in Australia.”

Professor Galea believes the best practical advice is for growers to:

• Avoid fields with a history of the disease
• Monitor the crop for early signs
• Apply preventative fungicides
• Avoid overhead irrigation in the afternoon
• Plough in crop debris soon after harvest
• Rotate your crops
• Use disease tolerant cultivars if available

See Also :

Lettuce Anthracnose Workshop – May 2011

Lettuce Anthracnose Poster – Feb 2008

For more information contact your Industry Development Officers :