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Melampsoridium betulinum

Rust of birch

Description

This heteroecious rust fungus begins its development in the spring on the needles of Larix decidua, initially forming spermogonia and later orange aecidia. Infection of birch leaves by aecidiospores leads to development of yellow, pustule-like uredospores; often over the entire underside of the leaf. In autumn, development continues with the production of teleutospores. The life cycle of the rust is completed with the formation of the next generation, basidiospores, which are budded off from the basidia in the spring. By overwintering in the birch buds, the rust can also survive without passing into the haplontic-state host (Larix spp.) and thus omit the formation of the spermogonia and aecidia (microcyclic development).