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This pine tree plant disease is caused by one of two species of fungi, either c. quercuum or cronartium harkenssii. It causes spherical swelling on the trunk of pine trees which often stunt or discolor growth beyond the gall, or swelling.
Pine tree branches which are infected with eastern and western gall rust will develop spherical swellings which are rough to the touch. These are often found on the main trunk of the tree as well as on the branches. The galls first appear in the spring and are a yellow or orangish color. On pine trees with gall rust, the growth of the pine tree beyond the gall will more often than not be stunted, discolored or distorted in appearance.
The two species have different life cycles. Western gall rust completes its life cycle with only one pine. Once it infects the individual pine tree, the spores of the rust can easily contaminate and begin to infect other nearby trees. Eastern gall rust, however, needs both a pine and an oak tree in order for its life cycle to be complete. Although it’s spores begin with an oak gall, spores can only infect pine trees. With Western gall, typically in early spring the yellow and orangish galls appear and moisture spreads spores when the temperatures become optimal. The spores then infect pine tree tissue which in turn causes an increase and swellin of the number of plant cells. Following this, in six months to a year a growth will form. The galls then grow and produce spores within the next two years. With Eastern gall rust the galls form only on oak. It is their spores which infect pines.
The stunted growth in both pines and oaks is caused by the gall rust infection which disturbs sap production causing distortions and bizarre growth patterns. Some people actually like the bizarre shapes this produces on their trees. However, if you prefer a truly healthy tree, unfortunately the only cure for gall rust is to prune off branches when you find them infected prior to the time when the galls produce spores in early spring and may infect nearby pine trees as well.
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