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Beginner

Scientific Name: Elsinoe veneta

Identification

• Very serious on black and red raspberries.
• Infects canes, leaves, petioles and fruit.
• Fungus produces small, grey lesions with purple borders, that measure approximately 3 to 10 mm in diameter.
• First infections usually occur on new primocane growth.
• Infected canes show lesions at the base of the cane early in the season and further up the cane later in the season.
• Lesions appear as small, rough sunken cankers on overwintered  canes.
• Lesions expand and join together, girdling the cane, causing drying and cracking.
• Infected canes are more susceptible to winter injury and the fungus overwinters, weakening new growth in the spring.
• Fruit symptoms include shrunken brown drupelets or withered, dry seedy fruit.

Often Confused With
Raspberry leaf spot
Botrytis grey mould
Spur blight

Period of Activity
Most infections occur in spring and early summer when the weather is wet.   Young green tissue is most susceptible to infection. Fruit is infected during the green fruit stage.

Scouting Notes
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.

Thresholds
None established.  

 

Advanced

Scientific Name: Elsinoe veneta

Identification
Anthracnose, caused by the fungus Elsinoe veneta,  is very serious on black and red raspberries. It can infect canes, leaves, petioles and fruit.

The fungus is active early in the season and first infections usually occur on new primocane growth. 

• On primocanes  anthracnose lesions appear as small, angular grey lesions with purple borders, approximately 3 to 10 mm in diameter. As the cane grows, early infections are evident as lesions at the base of the cane. Infections which occur later in the season are found further up the cane.   Several lesions may expand and coalesce as the cane grows, girdling the cane and causing it to dry out and crack. Infected canes are more susceptible to winter injury and produce weak growth in the spring.
• On overwintered canes, anthracnose lesions appear as small, rough, sunken cankers. New infections on these overwintered canes develop into small lesions with purple borders on leaves, petioles, and flower buds. Fruit symptoms include shrunken brown drupelets or withered, dry seedy fruit.

Often Confused With
Raspberry leaf spot
Leaf spot lesions are similar in size and shape to anthracnose leaf spots. The border around lesions caused by raspberry leaf spot is less purple and more brown. Raspberry leaf spot lesions often produce holes as infected tissue drops out. Raspberry leaf spot occurs only on foliage, while anthracnose infections are also found on petioles and canes adjacent to the infected leaves.   

Botrytis grey mould
On primocanes, cane botrytis lesions are larger and brown, while anthracnose lesions are grey with a purple border. On fruit, botrytis lesions develop grey, fuzzy spores, while anthracnose produces shrunken brown drupelets.

Spur blight
Spur blight lesions are purple to brown, triangular in shape and are found just below the leaf or leaf bud. Anthracnose lesions are grey with a distinct purple border, rectangular or oval in shape.

Biology
The fungus Elsinoe veneta overwinters as mycelium on canes that were infected in the previous growing season.

In spring, ascospores (primary spores) are forcibly discharged from infected tissue by rainfall. Throughout spring and summer, conidia (secondary spores) are produced and spread from diseased tissue to new growth by windblown or splashing rain. Both conidia and ascospores can germinate within 3-12 hours of wetness, and infect young green tissues. Anthracnose lesions typically develop a few weeks after an infection period.  Spots and lesions develop on primocanes, leaves, petioles and fruit.  On primocanes, anthracnose lesions can enlarge over time and may girdle the infected cane or cause it to crack and dry out.  Severely infected canes are more susceptible to winter injury. 

Fruit infections occur when there is abundant inoculum and wet weather during the green fruit stage.

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 3-12 hours of wetness; only very young green tissue is infected.

Scouting Notes
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.

Thresholds
None established.  

Management Notes

• Early infection is worst, late infections cause less damage.
• Early fungicide applications are important. See the Raspberry Calendar in OMAFRA Publication 360: Fruit Crop Protection Guide (Chapter 3 Berry Crops).
• Boyne, Kilarney, Qualicum 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.