|Maple tree infected with many Phomopsis galls|
Phomopsis galls are spherical wood balls growing on tree trunks or branches. Galls may be as small as a pea or up to 10 inches in diameter. In most trees, the galls look like a cluster of small nodules or bumps, all pushed together into one lump like a popcorn ball. In maple trees, however, galls often start as smooth round balls and become rough with age as the bark cracks. In all cases, the galls are made of hard disorganized wood that may be difficult to cut through. Examination of young growing gall tissue under a microscope reveals strands of fungal mycelia growing within the wood, but signs of the fungal pathogen are rarely visible to the naked eye.
It is common for a tree to have many galls scattered throughout the branches. Galls may occur individually on branches or be clustered together in small groups. Often one or a few trees in an area will be heavily infected with phomopsis galls and nearby neighbors of the same species will be completely healthy and gall free. Heavily infected trees may have slower growth than their uninfected neighbors. Small twigs that are girdled by one or more galls can be killed. Typically however trees with phomopsis galls are able to continue to grow despite their unusual appearance.
|Phomopsis galls on maple|