Norway spruce, white spruce and white fir would be much better choices. However, it is no longer advisable to plant Colorado blue spruce or Douglas fir since they are not well adapted to Pennsylvania’s moist, humid growing season. When establishing new spruce or fir tree plantings, place them in locations where good air circulation is available. If trees are in a landscape with a sprinkler irrigation system ensure it is not spraying onto the needles. This will also provide proper growing space to accommodate mature tree size. This means that densely planted trees should be thinned out by removing select trees. Affected needles eventually fall.Īs a preventative, ensure trees are widely spaced to provide good air circulation throughout the canopy. These yellow spots enlarge, becoming reddish brown patches on otherwise green needles. Ultimately the tree may decline to the point that it can no longer survive.ĭouglas fir affected by Rhabdocline needle cast develop yellow spots on the previous year’s needles from March through May. Branch die back begins to occur if the majority of the tree’s needles are infected for 3 to 4 years in a row. This gives the tree a thin, unhealthy appearance, typically with only the current year’s growth remaining on the tree. Rhizosphaera also affects white spruce and Norway spruce, but it is less common and generally only happens when they are grown under stressful conditions.Īs the name implies, needle cast diseases cause the needles to turn brown and fall off. On spruces, including Colorado blue and Engelmann, the needle casting disease is called Rhizosphaera. Both Rhabdocline and Swiss needle cast can affect Douglas fir. A number of needle cast diseases are affecting fir and spruce trees.
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