Dothistroma needle blightĪustrian pine is commonly affected by Dothistroma needle blight. In addition, several possible fungal pathogens can cause these symptoms as well. Winter burn occurs frequently on dwarf Alberta spruce but can occur on other conifers as well. In some cases, trees will have a snowline below which no damage occurs since those needles were under snow when the rest of the tree was drying. The most common symptom of winter burn is brown or red foliage on the exposed (often south) side of the tree. Many conifers are subject to needle drying of winter burn during the winter. Sensitive trees such as white pine can usually survive one-year’s damage but repeated acute damage can ultimately disfigure or kill trees.Īnother culprit is winter injury. Acute damage caused by direct salt exposure is easy to spot since the damage is usually greatest on the side of the trees facing the road. Many plants, especially eastern white pine, are sensitive to salt spray from roadways. Road crews apply sodium chloride and other deicing materials to keep roads clear in the winter. Photo by Bert Cregg, Michigan State University.Ĭonifers located along the road can be damaged by road salt. Environmental – related issues Road salt damage on white pine. Photo by Bert Cregg, Michigan State University. Pine identification left to right: Scots (Scotch) pine, Austrian pine, eastern white pine. Older Scots pines have orange-reddish bark, whereas the bark on Austrian pines is grey. Scots pines have shorter (1 1/2'” or less) needles and smaller cones than Austrian pines. Hard pines have two or three needles in each fascicle. Austrian pine and Scots pines are part of group known as hard pines along with our native jack pine and red pine. White pines have long (4” or longer), slender cones. The needles are thin and soft and often pale green. White pines have five needles in each fascicle. Determining the number of needles in a fascicle is the first step in identifying pines. Unlike many other conifers, needles on pine trees are clustered together in groups called fascicles. The most common pines in residential and commercial landscapes in Michigan are eastern white pine, Austrian pine and Scots (or Scotch) pine. Depending on the type of pine tree, there are several common causes of needle browning in pines. The fungus requires mild temperatures and long, continuous periods of high humidity for host infection and disease development.As spring arrives, we begin to see browning of pine needles in plantations, landscapes and along roadsides. Infections usually occur in crowded seedling beds, where humidity is high. Perithecia produced on infected seedlings or nearby trees release airborne ascospores, which begin new infections. Ascospores produced in the perithecia are dark brown, nonseptate, fusoid, and 23-26 x 9-10 microns. As the mycelium ages, it turns brown and flattens to form a wet mat of needles and fungal mycelium, upon which form conspicuous groups of black, round, beaked perithecia (fig. The infected needles turn yellow, die, and eventually fall off (fig. Look for the characteristic white fungus mycelium covering the needles and small branches in the lower, inner portion of infected seedlings (fig. More frequently, however, it causes extensive defoliation. The disease can cause seedling mortality. This disease is found in coastal California, Oregon, Washington, and British Columbia. Rosellinia needle blight, caused by the fungus Rosellinia herpotrichoides, has been reported on Douglas-fir and Sitka spruce.
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