Notes on Raspberry Diseases: Anthracnose

Identification

Purple spots with grey-white centres form on new canes, leaves and petioles. Spots enlarge on canes to form sunken pits. On second-year canes, these lesions can coalesce into cankers that girdle the cane and cause it to dry out and crack. Infected canes are more susceptible to winter injury and produce weak growth in the spring. Fruit infections occur when there is abundant inoculum and wet weather in the green fruit stage. Fruit symptoms include shrunken brown druplets or withered, dry seedy fruit.

Anthracnose disease on raspbery primocane

Anthracnose disease on raspbery primocane

Anthracnose infection on leaves

Anthracnose infection on leaves

Period of activity

Ascospores are rain-splashed and air-borne from infected canes in early spring. Conidia are rain-splashed from overwintering infected canes in the spring and throughout the summer to new growth. Infection requires three to twelve hours of wetness; only very young green tissue is infected.

Anthracnose on overwintering fruiting cane

Anthracnose on overwintering fruiting cane

Monitoring

In early spring, look for lesions on overwintering canes which indicate the potential for problems. From spring through to bloom, check primocanes and developing laterals for purplish spots with grey-white centres.

Management notes

Early infection is worst, late infections cause less damage. Early fungicide applications are important. See the Raspberry Calendar. Boyne, Kilarney and black and purple varieties of raspberry are very susceptible. Keep rows narrow and control weeds to improve drying in the row. Dispose of pruned canes. Destroy wild brambles in the vicinity to eliminate other sources of infection.

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For more information:
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E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 17 May 2006
Last Reviewed: 17 May 2006