PROBLEMS OF CRABAPPLE TREES
Apple Scab & Cedar Apple Rust
WHAT YOU’LL SEE…are dark olive colored spots on both sides of the leaves and may also exude orange rust spots. In moist weather, the spots may combine and overtake the leaf due to fungal mycelium growth. Occurrence of the fungus will occur in the spring at the time of, or just after leaf break when the leaves are thin and lack the production of leaf hairs which help hold moisture off the leaf surface. Severe infections cause massive yellowing and almost complete canopy loss by August however this does not mean the tree is about to die.
THE REASON FOR THE PROBLEM…is a genetic problem that allows humidity to penetrate newly developed leaves. Once moisture has been on a leaf surface for more than 24 hours infection begins to occur. Active fungi spores can then also can be carried by the wind from other areas of the yard and neighborhood infecting other Crabapple trees especially during very wet seasons. Junipers are the host plant of Cedar Apple Rust so in order for the disease to exist both Junipers and Crabapples or Apple trees must be present.
THE BEST WAYS TO CONTROL Applescab DISEASE…is to plant resistant varieties of trees. But since your tree is already planted, the next best thing is to be sure all fallen leaves are cleaned up and disposed of each fall. While you have no control over what may blow in from neighboring areas, at least be sure the area immediately surrounding your crabapple is clean. Cut down and remove any Junipers if the infection is very severe.
OTHER OPTIONS AVAILABLE TO YOU…include protective fungicide applications developed for Applescab disease. The first application should occur just after the leaves appear, with two additional applications following during the summer. While good control of this fungus can be achieved, total eradication of the disease with fungicide applications is not realistic. Crabapple trees can also be injected during August with fungicides to provide control of crabapple disease for the following spring. It is important to note that not every cultivar responds the same way to the injections so our Certified Arborists would need to visit your property to determine if injections can play a role in controlling the disease without having to spray.
Posted on: August 4, 2015
What you’ll see…is wilting leaves and dieback of branches, often one at a time or on one side of the tree. This can occur over a number of years, with remiss...