| Gooseberry and Currant -- Blister Rust |
| See Also: Pine, White -- White Pine Blister Rust |
| Cause:
Cronartium ribicola, a fungus that attacks both wild and cultivated species of gooseberry and currant. The black currant (Ribes nigrum) is more susceptible than the red (R. sativum). The red currant cultivars 'Viking' and 'Red Dutch' are practically immune. The wild species stink currant (R. bracteosum), flowering currant (R. sanguineum), Sierra gooseberry (R. roezli), and Sierra currant (R. nevadinse) are very susceptible. The white or five-needled pine is an alternate host for the fungus. Rust of white pine has caused severe losses. Susceptible currants and gooseberries cannot be planted safely nearer than 1,000 ft and preferably 0.5 mile from white pine.
In spring, spores form in orange pustules (aecia) on tree cankers. Wind distributes aeciospores to currants and gooseberries. Uredia form on the underside of these Ribes hosts and produce urediospores. The urediospores can only reinfect more Ribes hosts and con-tinue to do so during the rest of the growing season. Telia form in late summer where the uredia are located. The teliospores are not dispersed but germinate to form another spore type called a basidiospore. These spores are blown to white pine, causing new infec-tions. Pycnia appear on the bark the following spring. Aeca erupt from the same area where the pycnia formed the previous year. Aeciospores are produced perennially until the branch dies. |
| Symptoms: On the undersurface of affected currant leaves, small cuplike spots (uredia) develop. Spots are slightly raised and yellow-orange. Later in the growing season, brownish hair-like structures (telia) develop in the same or new lesions. Defoliation of infected hosts is common. |
| Cultural control: Remove white (five-needled) pines within 1000 ft of planting. |
| Content edited by: Jay W. Pscheidt on January 1, 2009 |
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