Ask the Arborist with Forester Jeff: What is Apple Scab?

Today we look at another problematic disease that affects both Apple and Crabapple trees.  Apple scab is a fungal disease of the  Malus tree species (both Apple and Crabapple).

According to "Wikipedia" apple scab  (Venturia inaequalis) creates dull black lesions (spots) on the leaves.  Often heavy infected trees will produce yellow leaves (see photo) with dark spots, which result in premature leaf drop and reduced tree aesthetics.

Apple scab overwinters in fallen Apple / Crabapple tree leaves that have retained the  inoculate .  Apple scab operates very similar to Cedar Apple Rust (which we discussed yesterday) with heavy spore release in wet springs.  Apple Scab unlike Cedar Apple Rust has only one host tree that being the Apple / Crabapple trees.  There are preventative fungicides which can be applies as the new leaves emerge to leave a protective leaf coating that hence prevents germination of Apple Scab into the unsuspecting Apple / Crabapple leaves.

I recommend a minimum of two fungicide applications to provide adequate protection for your Apple / Crabapple trees.  Today we have over 600 different varieties of Apple / Crabapple trees, many of which have been genetically crossed to provide added resistance to Apple Scab.

When making a decision on planting an Apple / Crabapple tree you would greatly benefit from selecting varieties that are Apple Scab and Cedar Apple rust resistant.  Contact your local Yacko and Sons Tree Service staff Forester for additional information on proper tree selection.

And remember contact Forester Jeff for your FREE TREE LOOK-UP FROM THE TRUNK-UP! and receive your official Yacko and Sons Tree Service green and yellow Frisbee Free!