Black witch's butter

Black witch's butter (Exidia glandulosa) is a jelly fungus typically classified as a saprotrophic species that colonizes decaying wood. While it primarily feeds on dead organic matter, its appearance on living trees often indicates that the host plant is suffering from underlying health issues, bark damage, or significant structural decline.

The fungus is a basidiomycete that thrives by breaking down woody tissue. From an agronomical perspective, it is viewed as a colonizer of weakened hosts. When found on living trees, it indicates that the tree's natural defense systems are compromised, allowing the fungus to exploit necrotic tissue, frost cracks, or wounds left by improper pruning or pest infestation.

Symptoms are easily identifiable during wet weather: the fungus forms distinctive, black, gelatinous, and brain-like structures on the bark. These sporocarps are covered in small pimple-like bumps (glands). During dry periods, the fungus shrivels significantly, turning into a thin, dark, crust-like residue that is easy to miss but reactivates immediately when moisture returns.

Development and spread are facilitated by high humidity and poor air circulation. Spores are dispersed through the air and rainfall, settling in microscopic cracks or damaged areas of the bark. Once established, the mycelium can persist in the wood, taking advantage of the tree's inability to isolate the infected area due to stress, lack of nutrients, or environmental neglect.

Prevention focuses on bolstering tree vigor and maintaining structural integrity. Effective management includes regular sanitation: removing deadwood, pruning infected branches, and protecting wounds with fungicides or wound paint. Proper soil fertilization and irrigation are also essential, as a healthy, vigorous tree is much more capable of naturally resisting colonization by opportunistic fungi like Exidia glandulosa.