Cause Sphaerulina taxi, a fungus that has been reported from all states and considered common in Washington. A problem when yew is used as a hedge.
Symptoms The needles of the current season are killed. Infected needles become light green and finally grayish or reddish brown. The upper surface of an infected needle is covered with minute black fruiting bodies (perithecia) of the fungus. The infected needles are cast.
Cultural control
- Rake and destroy fallen leaves.
- Avoid overhead irrigation or any practice that keeps plants wet for extended periods of time.
Reference Shaw, C.G., and Harris, M.R. 1960. Important diseases and decays of trees native to Washington. Ag Extension Service, WSU. Extension Bulletin 540.