Cause Elsinoe necator, a fungus that overwinters on infected canes. Blackberry-raspberry hybrids such as 'Boysenberry' and 'Loganberry' are not often infected. The disease is not always severe enough to warrant the cost of spraying. This disease is particularly serious if rains continue late into spring, when spots on canes may be plentiful enough to retard sap flow, thus girdling the canes. Early-season infections are more severe than late-season infections.
Symptoms Small purple spots appear on canes, increase in size, and develop light-gray centers with brownish-purple borders. Spots commonly coalesce to form large irregular lesions. Numerous lesions may girdle the cane causing it to dry and crack. On leaves, minute purple spots develop, which enlarge and coalesce to form gray to white areas. Such areas may drop out. Partial defoliation may result. Berries may ripen prematurely and be small and dry.
Cultural control
- Plant certified disease-free stock.
- Prune off old cane stubs after planting.
- Prune off old canes close to the ground as soon after harvest as possible, and destroy by burning. Best done before rains resume in the fall.
- Early primocane control through chemical burning.
- Thin out weak canes. Eliminate weeds to provide good air movement.
- Avoid overhead irrigation, or limit the time plants are wet from irrigation.
- Remove wild brambles near commercial plantings.
Chemical control
- Late dormant or delayed dormant. Further control not needed in most years.
- Bordeaux 8-8-100. O
- Rex Lime Sulfur Solution (28%) at 6 to 12 gal/100 gal water. 48-hr reentry. O
- Fixed coppers such as Nu-Cop, C-O-C-S, Nordox, Cuprofix, or Kocide most with a 48-hr reentry. Liqui-Cop for the home. H O
- Sulforix at 3 gal/100 gal water. 48-hr reentry.
- Applications when new canes are 6 to 12 inches high may be effective if disease pressure is great.
- Abound at 6 to 15.5 fl oz/A. Do not apply with silicone-based surfactants. May be applied on the day of harvest. Group 11 fungicide. 4-hr reentry.
- Bonide Captan 50 WP at 3 Tbsp/gal water can be used in home gardens. Do not use within 3 days of harvest. H
- Rex Lime Sulfur Solution (28%) at 0.5 to 1.25 gal/100 gal water. 48-hr reentry. O
- Cabrio EG at 14 oz/A. May be used at harvest. 12-hr reentry.
- Captan 80 WDG at 2.5 lb/A. Do not apply within 3 days of harvest. Group M4 fungicide. 48-hr reentry.
- Pristine at 18.5 to 23 oz/A. Do not use with any other tank additive. Can be used day of harvest. Group 7 +11 fungicide. 12-hr reentry.
- Quadris at 6 to 15.5 fl oz/A. Do not apply with silicone-based surfactants. May be applied on the day of harvest. Group 11 fungicide. 4-hr reentry.
- QuiltXcel at 14 to 21 fl oz/A. Do not use within 30 days of harvest. Sprayers should not be used on apples. Group 3 + 11 fungicide. 12-hr reentry.
Note: Switch is registered for anthracnose caused by Colletotrichum spp. and it is not clear if it would be effective on anthracnose of blackberry.
Some registered products offer only suppression of this disease and thus are not recommended for use. These products include Tanos.
References Martin, R.R., Ellis, M.A., Williamson, B., and Williams, R.N. 2017. Compendium of Raspberry and Blackberry Diseases and Pests. 2nd edition. St. Paul, MN: APS Press.
Sivanesan, A. and Critchet, C. 1976. Elsinoe veneta. CMI Descriptions of Pathogenic Fungi and Bacteria, No. 484. Surrey, England: Commonwealth Mycological Institute.