Dogwood Anthracnose Discula destructiva is a killer disease of dogwood trees in the United States.  It starts with spots on the leaves and flower bracts, then spreads to the twigs and branches.  The speed at which the disease progresses is dependent on weather and tree health.  Healthy trees are able to withstand infections better than weak trees.  The best defense is good cultural practices.  Trees should be planted in the right location with proper sun exposure and soil requirements.  They should be mulched, fertilised, pruned (removal of infected material), and watered during prolonged periods of little water.  Daniel Gillman, UMass Extension