Saturday, July 3, 2010

Viburnum Bacterial Blight by Mary Small

If your viburnum leaves are sporting brown and yellow speckles, better get out the pruners!  These leaves are infected with Pseudomonas blight, a bacterial disease.  Cool moist spring weather is partially responsible for its appearance this year.
The disease over-winters on buds and twigs.  During springs like we just had, bacteria is splashed from the wintering sites to the leaves, creating brown, angular spots often surrounded by a yellow “halo”.  In severe infections, leaves become distorted and twig tips may die.
Prune out the damaged areas, disinfecting your pruning tool between each cut with rubbing alcohol, a 1:9 bleach/water solution or a disinfectant spray.  The treatment helps prevent accidental bacterial introduction to healthy tissue.
Also take time to thin or prune the affected viburnum so there is better air movement in the canopy of the plant- which also helps reduce infection.