Cause Mechanical injury, winter injury, chemical injury, insect damage, fungal diseases, or improper growing conditions. Gumming often follows brown rot, or shothole (peach, apricot), twig infections. Botryospheria spp and wood decay fungi can also result in gummosis (among other symptoms) and yield reductions of 12% to 22%. The disease bacterial canker, caused by Pseudomonas syringae, also can produce a severe gumming of sweet cherry and some other stone fruit trees. However, gumming also may be spontaneous, especially in trees that have made a forced growth due to too much water or nitrogen fertilizer, or both. Sweet cherry trees in wet or other unfavorable locations are particularly liable to gummosis. Sweet cherry trees treated with ethephon to loosen fruit or stimulate flowering can develop a clear gummosis.
Symptoms Gum exuding from buds, twigs, branches, or trunks. Pools or large deposits of gum collect beneath the bark at the crotch, on larger branches, or on the trunk. Gum eventually breaks through to the surface and runs down the bark.
- Control insects and fungus diseases.
- In large cankers, cut away all dead tissue until a sound surface is exposed. Treat the wound with a reliable disinfectant.
- Follow cultural practices that produce a firm, stocky, moderate growth rather than a forced growth of soft wood.
- Prevent trunk injury when possible. Whitewashing or shielding trunks from the sun can prevent winter injury.
References Ezra, D., Hershcovich, M., and Shtienberg, D. 2017. Insights into the etiology of gummosis syndrome of deciduous fruit trees in Israel and its impact on tree productivity. Plant Disease 101:1354-1361.