Cause Drepanopeziza ribis (asexual: Gloeosporidiella ribis), a fungus that overwinters on dead leaves. Small, mushroom-like fruiting bodies (apothecia) develop on fallen leaves in spring. They produce airborne ascospores that infect newly developing leaves. Rainy weather favors spore release and infection. Different fruiting bodies (acervuli) are produced in 3 to 4 weeks after ascospore infection. Acervuli produce conidia, which are rain splashed and infect healthy leaves. The disease is serious in wet seasons. Older leaves of black currant were shown to be more susceptible to infection than younger leaves.
Symptoms Small, dark-brown, round or irregular leaf spots develop, which, when abundant, may cause foliage to yellow and drop by midseason. Small, grayish bodies (acervuli) develop in leaf lesions. The disease reduces the plant's vitality, growth, and productiveness.
On currants, fruit as well as leaves may show spotting like fly specks. Severely infected berries crack open and drop.
- Remove and destroy dead leaves from under bushes.
- Cultivate under and around bushes to bury leaves before budbreak in spring.
- Prune and thin bushes to provide better air circulation and drying conditions.
Chemical control Starting when the first leaf reaches full size, apply during wet spring conditions until dry weather prevails in summer. Tank-mix and/or alternate products from different groups with different modes of action to prevent the buildup of resistant fungi. Limit the use of any one group during the growing season.
- Abound at 6 to 15.5fl oz/A. Do not apply with silicone-based surfactants. May be applied on the day of harvest. Group 11 fungicide. 4-hr reentry.
- Cabrio EG at 14 oz/A. May be used at harvest. Group 11 fungicide. 12-hr reentry.
- Copper-based products. Group M1 fungicides. O
- Badge X2 at 4.25 to 9 lb/A. 48-hr reentry.
- Bordeaux 8-8-100.
- Champ WG at 5 to 8 lb/A. 48-hr reentry.
- Copper-Count-N at 5 to 10 quarts/A. 48-hr reentry.
- Cuprofix Ultra 40 Disperss at 6.25 lb/A. 48-hr reentry.
- Kocide 3000 at 4.25 lb/A. 48-hr reentry.
- Nordox 75 WG at 3 to 6.5 lb/A. 12-hr reentry.
- Nu-Cop 50 DF at 5 to 8 lb/A. 48-hr reentry. O
- Previsto at 1 to 2 quarts/A. 48-hr reentry.
- Mettle 125 ME at 3 to 5 fl oz/A. Do not apply within 14 days of harvest. Labeled only for Gooseberry. Group 3 fungicide. 12-hr reentry.
- Omega 500 F at 1.25 pints/A. Pest is not on the label but may be effective. Do not use with an adjuvant or within 30 days of harvest. Group 29 fungicide. 12-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.
- Proline 480 SC at 5.7 fl oz/A. Do not use within 7 days of harvest. Group 3 fungicide. 12-hr reentry.
- Propulse at 13.6 fl oz/A. Do not use within 7 days of harvest. Group 3 + 7 fungicide. 12-hr reentry.
- Quash at 2.5 oz/A. Do not use within 7 days of harvest. Group 3 fungicide. 12-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.
- Rally 40 WSP at 5 oz/A. Applications may be made up to the day of harvest. Group 3 fungicide. 24-hr reentry.
- Rex Lime Sulfur Solution (28%) at 0.5 to 0.75 gal/100 gal water. 48-hr reentry. O
- Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 1.25 fl oz/gal water. May be applied up to the day of har-vest. Group 3 fungicide. H
- Switch 62.5 WG at 11 to 14 oz/A. May be used up to and including the day of harvest. Group 9 + 12 fungicide. 12-hr reentry.
Reference Xu, X.M., Robinson, J.D., and Berrie, A.M. 2009. Infection of blackcurrant leaves by Drepanopeziza ribis in relation to weather conditions and leaf position. Journal of Phytopathology 157:280-286.