slowing death of a crab apple tree.
we've got a 12 year old (best guess) crab apple tree. we planted it 5 years ago where an old walnut tree was that we'd recently removed. the trunk's 3 - 4 " in diameter. the crab apple tree appeared to be quite healthy - until mid summer this year. leaves started falling off about 1/5 of the branches. now those branches are bare, dry, brittle and appear to be very dead. the bark is split on those branches (and part of the trunk). this "blight" appears to be spreading. any idea what this is or how we should treat it ?
Crab apple trees are sensitive to juglone, a toxic substance produced by walnut trees. It can cause stunted growth, yellowing of leaves, premature leaf drop, and eventually death. Some plants may survive for years near a walnut tree, but will wilt and die as the tree increases in size. .This is also true even when the walnut tree has been removed. Any remaining roots may still exude toxins for several years as they decay. There is no cure for this toxicity. Juglone will eventually breakdown in soil, air, and water. How fast that happens depends on the extent of root decay, and environmental factors.
That being said, the symptoms could be confused with various wilts and other bacterial or fungal pathogens that exhibit the same symptoms such as apple scab and fire blight. If this is the case, you may want to try removing all the fallen leaves from the area this fall, as the spores will over-winter in the leaves and re-infest the tree next year. Eliminating this exposure will help minimize the fungus exposure and allow the tree to rebound - assuming this is a fungal problem and not the juglone from the pre-existing walnut tree. Call our extension office if you would like more information on this problem - 641-423-0844 Cerro Gordo County.
I hope this helps you.