There are numerous species of rusts that appear on pine trees in our region. The most commonly found rust on ornamental plantings is western gall rust, caused by Endrocronartium harknessii. The fungus produces galls at infection points on twigs or small branches. The galls are conspicuous in June/July when bright orange spores are produced on the gall’s surface. This disease does not usually kill mature trees but it does kill branches and reduce vigour. If the gall forms on the central growing stem, it will weaken the wood and the trunk may break in the wind.

Control

This rust occurs locally and does not require an alternate host; therefore, it can spread easily from pine to pine. Control can be accomplished by pruning out the galls and burning or disposing of them in the garbage. Prune back 15 cm (6”) from the gall or to the next lateral branch to maintain form. Sterilize pruning tools between cuts with gasline antifreeze.

Western gall rust killing a branch
Western gall rust infection
Western gall rust infection