Continuing on the bitter cherry (Prunus emarginata) theme:
The yeast-like sac fungus Taphrina confusa induces witches’ brooms on several Prunus species. Although the western choke cherry (P virginiana) and Sierra plum (P subcordata) are most often infected, Leonard and I found this bitter cherry with a witches’ broom along Modoc National Forest Road 40N11 near Adin CA (Modoc County).
Witches’ brooms usually involve a dense group of small branches and shoots emanating from a common point forming broom like clusters.
T confusa, Prunus witches’ broom fungus, spores are forcibly discharged from the infected tissues of a witches’ broom in late spring or early summer and are spread by wind and rain. Spores land and remain on the twigs and bark of a Prunus host until the cool, wet weather of the following spring when they germinate and produce fungal threads called hyphae. Hyphae combine to form mycelial threads that penetrate the host inducing witches’ brooms and drawing nourishment from the host. A single layer of microscopic, spore-producing sacs develops on the infected plant swellings. Upon maturity the spores are again released from the host and begin the cycle anew.
Even though T confusa is found throughout the United States, there are localized concentrations in certain areas, one of which is near Mount Shasta in California.