![]() ![]() ![]() Here are five of the most common fir tree diseases and how to recognize their signs and symptoms: Swiss NeedlecastĪ disease that only affects Douglas fir trees, Swiss needle cast has begun to spread more and more in the Pacific Northwest. The first step is to educate yourself usually, it’s easy to recognize the signs and symptoms of a common tree disease if you know what to look for. Fortunately, however, with a little diligence and the help of a good tree service, you can often arrest the progress of these diseases in their tracks. Unfortunately, for tree owners, fir trees are vulnerable to many ailments. Plant Disease 83:200.Nothing is more heartbreaking than watching your beloved fir tree waste away, and ultimately perish, from any one of the many common diseases that plague them. A new foliar blight of Douglas, grand and noble fir caused by a binucleate Rhizoctonia-like fungus. Registered for evergreen trees grown in greenhouse, or outdoor container, or field nursery. ProStar 70 WG at 3 to 12 oz/100 gal water.It has shown some symptom suppression when used before inoculation in the laboratory. Medallion WDG: Although fir is not listed on the label, if not phytotoxic, it can be legally used.However, laboratory studies have shown some symptom suppression when Bravo 720 was used before inoculation. Bravo products used for Swiss needle cast may still result in losses from this disease.Affirm WDG at 0.25 to 0.5 lb/100 gal water.Remove and destroy affected trees.Ĭhemical control Tactics have not been developed to control this disease. Look for areas of dead needles on the periphery of the tree. ![]() Scout trees before the first shearing of the year.Pruning low in trees that have the disease only in the lower branches may allow harvest at some future date.Control weeds around the bases of trees to improve air circulation.Avoid planting near native stands of Douglas-fir that appear to have this disease.Avoid planting in low-lying areas with poor air drainage.The disease, which can spread to affect as much as half the side of a tree, can be distinguished from Botrytis (gray mold) in that the latter affects only current-year needles and shoots. Buds and twigs of grand fir are killed but not those of Douglas-fir. Under moist conditions, fine fungal webbing may be visible, binding together the discolored needles. Needles hang down and stay attached to the branches long after they have died. Affected needles turn brown without any associated yellowing or banding. Browned areas can be anywhere on the tree but most often are on lower branches. Symptoms The disease usually is first noticed as browning of outer foliage in a roughly circular area. Disease severity and symptom development are related to drought conditions. Infected needles are thought to be blown onto healthy trees where the fungus colonizes healthy needles during the rainy season. This needle blight has been found in native Douglas-fir trees bordering Christmas tree plantations. Although the Rhizoctonia-like fungus can infect needles of all ages, new infections are typically seen only on current year needles. The disease is worse in Christmas tree plantations with restricted air flow, close tree spacing, and dense foliage. Some studies have shown balsam fir and Sitka spruce may also be susceptible. Concerns about the disease in western Hemlock increased substantially in 2019. ![]() The disease affects grand, noble, and Douglas-fir. Cause A binucleate Rhizoctonia-like fungus, but not the same one that causes root rot or damping-off of seedlings. ![]()
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