Spruce Needle Cast Disease
Spruce needle cast disease is a common fungal disease of spruce trees in Minnesota. Needle cast is a general term used for several different types of fungal diseases including rhizosphaera needle cast and stigmina needle cast. Both of these diseases cause the needles on the lower and inner branches of spruce trees to turn brownish purple by late winter or early spring and fall off the following summer. This leaves spruce trees with very thin to bare branches starting at the bottom of the tree and moving up the tree each year. Newly growing needles at the tips of branches do not show symptoms.
The fungal spores that cause this disease are contained on infected needles. As the needles are expanding in late spring, these spores are carried with the wind and splashing rain or irrigation to infect new needles. It is during this infection period that the new needles should be protected with fungicides to prevent further infection. After the needles have fully emerged, they are no longer susceptible to infection.
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