Phomopsis canker & gall
The fungus Phomopsis can cause disease in a number of plants, including Russian olive and hickory. Symptoms of infection vary depending on the host plant. Phomopsis causes sunken areas called cankers to form on the branches and trunk of Russian olive, while galls (swellings) form on the branches and trunk of hickory.
Phomopsis canker of Russian olive is caused by Phomopsis arnoldiae. The fungus survives in cankers on the trunk or branches and produces spores throughout the growing season, which are thought to be wind- blown or rain-splashed to nearby trees. The fungus then enters the tree through wounds. Small cankers appearing on branches are reddish brown to black, while larger cankers on the trunk are dark colored, sunken, and split open. Sap may ooze from the canker margins. Sometimes wilting and branch die back may occur as the canker girdles the branch or trunk. Eventually, black, pimple-like reproductive structures are produced on cankered tissues. These structures produce spores that infect wounded tissue.
Phomopsis gall of hickory is caused by several different species of Phomopsis. It is not known how the disease infects, but infection may occur at any time throughout the growing season. It is thought that fungal spores initially enter young twigs through wounds and the fungus then progresses into the branches. Phomopsis of hickory causes round swellings on the branches or trunk called galls. Galls can occur singly or in clusters and range in size up to 25 cm in diameter. When multiple galls occur, small branches may be girdled and killed. Attached galls eventually die after several years and turn black in color.
There are no chemical controls for Phomopsis canker or gall. Cultural practices should include increasing tree vigor by watering during dry periods, mulching, properly pruning, and fertilizing when necessary. Remove and dispose of all diseased branches. Branches should be pruned during dry periods at least six inches below the gall or canker margin. To prevent initial infections, avoid wounding trees.