|Spruce buds opening. M. Grabowski, UMN Extension|
Spring is here and spruce trees are opening their buds and developing young new needles. Now is a critical time to inspect spruce trees for Rhizosphaera needle cast, a common disease of spruce trees in Minnesota. Rhizosphaera needle cast is caused by the fungus Rhizosphaera kalkhoffii. This fungus infects the young growing needles of Colorado blue spruce, white spruce and Norway spruce. New infections do not have obvious symptoms and many gardeners do not recognize the disease until it is too late to prevent new infections this year.
What to look for
|Discolored needles with black spore producing structures. USDAFS|
Help for sick trees
|Spruce Needles at half their mature length. M. Grabowski|
If left untreated, infected needles will die and fall off after 1 year. If a branch looses its needles 3-4 years in a row, the branch dies. Untreated trees often have dead branches on the lower part of the tree and infected branches higher up.
Preventing future problems
|Needle loss from Rhizosphaera needle cast, M. Grabowski UMN|