Foliar Diseases

The weather patterns of 2009 and early 2010 have created ideal conditions for some of the same foliage diseases that were rampant on many tree species last year.  Dogwoods, sycamore, cherry, crabapples and hawthorn were among the most heavily damaged by leafspot and anthracnose diseases. Conifers, especially spruce, pine and Douglas fir were widely damaged by needlecast diseases.

Foliage diseases will likely be severe again in the spring.  Here are some things you can do to reduce the impact:

• Rake up and destroy fallen leaves and dead needles that may accumulate within the crown of conifers.
• If the crown of the tree is very dense or shaded by other trees, pruning to thin a dense crown or raising branch levels on adjacent trees will improve light and air penetration into the canopy and help reduce new infections.
• Perform a soil test and provide optimum nutrient levels.  This will help suppress certain foliage disease and facilitate recovery should infection occur.
• Apply preventative fungicide treatment to trees that were damaged last year. Treatments should begin as new growth develops and be repeated during the spring as growth expands.  Certain diseases may require additional treatments in summer to maintain suppression.