Alder Cone Gall Fungus

Alders along the shore of Manzanita Lake (Lassen Volcanic National Park) are heavily infested with alder cone gall fungus.

Taphrina occidentalis is a sac fungus that induces flat, twisting galls on the bracts of alder cones. The cone bracts of infected cones expand into tongue-like shapes in late spring and early summer. These galls are usually green with red along the margins. However, in full sunlight the galls can turn completely red.

Fungi lack chlorophyll and cannot produce their own food. Sac fungi produce their spores in sacs and when mature the spores are forcibly ejected and float in the wind.

When a viable spore lands on the proper host under the correct conditions germination can occur.  In the case of alder cone gall fungus, all alder species (Alnus sp.) in the Western States, both native and ornamental, can be infected. Fungal threads called hyphae are formed. The hyphae singly or combined into mycelial threads penetrate into the host (cone bracts in this case) to obtain nourishment and in the process induce galls. By late August the galls begin to wither and turn brown ejecting spores. Released spores can overwinter and reinfect host trees the following spring.

I find all the weird gall shapes fascinating.

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