Gummosis

Gummosis is the exudation of gum or resin from the bark or wood of plants, usually as a response to wounding, stress, or infection. It is most commonly observed on fruit trees such as peach, apricot, plum, and cherry, and can also occur in citrus and grapevines. The condition is not a single disease but a symptom that can result from various underlying causes.

Causes of gummosis include a range of pathogens as well as abiotic stress. Fungal pathogens such as Cytospora spp. and Botryosphaeria dothidea are commonly implicated, as are Phytophthora species. Bacterial pathogens can also be involved in some cases. In addition, environmental factors like cold injury, drought, pruning injuries, improper cultural practices, or nutrient deficiencies can trigger gum production, especially when the plant is stressed or wounded.

Symptoms typically include visible gum oozing from wounds or cankers on the bark, often at the trunk or main limbs. The affected areas may become sunken or cracked, and cankers can expand, leading to twig dieback or reduced vigor. Gum exudation may be more conspicuous during wet conditions or in late winter to spring.

Diagnosis involves field observation of gum and cankers, followed by laboratory tests to identify the exact causal agent. Culturing, microscopy, or molecular methods may be used to confirm the pathogen. Management focuses on reducing stress and controlling infection, as there is no universal cure. Practices include pruning out infected wood with clean cuts, removing and destroying severely affected branches, sterilizing tools between cuts, improving irrigation and nutrition, and maintaining good drainage. Where appropriate, fungicidal or bactericidal treatments may be recommended by local guidelines, along with sanitation to prevent reinfection and the use of resistant cultivars when available.