Do you have a crabapple tree in your yard? Well, NOW is the time to take care of it. We receive many phone calls in the mid to late summer about crabapple trees. The conversations all seem to have the same start; “My crabapple tree looked so nice this spring and now it looks terrible. Why is that and what can be done to help it?” The tree has a fungal disease called scab. This is a potentially serious fungal disease of ornamental and fruit trees in the rose family. Trees that are most commonly and severely affected include crabapple, hawthorn, mountain ash, apple and pear. This disease is most severe in years with cool, wet weather, as the buds and blossoms are opening up. How is this spring adding up? It seems pretty cool and wet to me.
You will first notice scab on the upper leaf surface, as well as on the fruits. These lesions can be small, the size of a pinhead or as large as one inch in diameter. When the disease is severe, lesions can merge and cover a large portion of the leaf or fruit surface, defoliation of the tree will then follow.
The good news is that this disease can be controlled and if your tree is taken care of the leaves will stay on and will even have fall color. While many trunk and soil treatments are in testing stages, none seem to be a viable option at this point. Some trunk injections look promising; however drilling small holes into the trunk of a tree on an annual basis is not a good practice. As with most chemical products today, they only will last 7-10 days and then not be effective anymore. Thus, a program of 3 foliar sprays in the spring and early summer is the best approach. The timing of these applications is of utmost importance or they will not work. The new chemistry of the products we use provides effective control of an infection that occurred up to 10 days ago, and then 7-10 days forward. To cover our cool, damp springs, the 3 applications work great, and will aid the tree in holding the leaves all summer and into the fall. Proper thinning is also a great help in the control of this disease. If your tree is overcrowded in the canopy, the leaves will remain damp and this will accelerate the scab disease. I would suggest waiting until after flowering for any pruning of your crabapple.
If you can remember back to last summer, and if your crabapple tree looked sickly, NOW is the time to take care of it. By the time you begin to see the lesions it will be too late for this season. With the proper care, your tree should provide beauty to your yard all summer and even in the fall.
If you have additional questions, would like help or information on tree care, please contact a professional. Certified arborists must follow stringent safety and performance standards, are required to have insurance, and have a trained and professional staff that is dedicated to ethics and quality in business practices.
Written by Bob Gluck
Certified Arborist WI-0116A
Hoppe Tree Service