Pine-pine gall rust or western gall rust is found throughout North America on two- and three-needle species of pine (Pinus spp.).
Photographed along the boardwalk in Burns Bog on a shore pine (Pinus contorta var. contorta), this image shows a sporulating gall. The swelling of the branch that causes the gall started somewhere 2-4 years prior to this photograph being taken, when a nearby gall at this stage released its spores and one landed here when this branch was young. As the spore divided and grew into a mature rust fungus, it resulted in hormonal responses leading to hyperplasia (or increased cell proliferation), i.e., the formation of the gall.
Unlike many other rusts, western gall rust is autoecious, meaning it does not have an alternate host species (compare with white pine blister rust, which requires gooseberries as alternate hosts). Transmission is directly from pine tree to pine tree. Fortunately for natural stands, it has low lethality on established trees. However, it can be economically damaging in plantations or managed forests by decreasing wood volume through malformation (or in the case of Christmas tree farms, unsightly blemishes). As noted in the High Plains Integrated Pest Management Guide, it has the property of being very difficult to control “due to its high rate of infection and the latency period between infection and expression of the symptoms”, which sounds grimly familiar.
The Plant Disease Diagnostic Clinic of Cornell University has an excellent factsheet on pine-pine gall rust, while Forestryimages.org presently has 63 images of it and its expression in pine trees, including some images of young stems and established trunks with galls and burls.
Lastly, in UBC Botanical Garden news: the staff have collectively been making an effort to share more about plants and the Garden during this time. In addition to Botany Photo of the Day, also check out our gardening and plant help forums, our Instagram feed, or our being-revitalized Youtube channel.
Just released in the past 24 hours on Youtube, we have a previous year’s performance from a former artist-in-residence and a 360-degree virtual tour of the Greenheart Treewalk, both filmed in the David C. Lam Asian Garden. We hope in some small way this helps you to experience the health and wellness benefits of visiting a BC rainforest without leaving your home: