Crabapple trees come in all sizes, shapes and blossom colors. Choose from more than 30 species and 700 differing cultivated types. Used as an ornamental tree in yards across the country, this spring-blossoming tree is well liked because of its flower colors, sweet fragrance and colorful fruits. A crabapple tree ranges in height from 8 feet to over 40 feet and it is rated as a USDA Hardiness Zone 3 tree.
Common disease types associated with the crabapple tree include fire blight, apple scab, apple rust and powdery mildew. Fungus and bacteriainfecting the tree in various locations cause these. Some diseases can be seen on the leaves and others on the bark, branches, blossoms or spread throughout the entire tree. Most of the diseases can be avoided, prevented or maintained. The most important thing is to identify and know the characteristics of the disease and use the proper treatment.
Crabapple trees afflicted with fire blight will have leaves and newly appearing shoots that seem to be burned by fire. This bacterial disease can spread from flowers to twigs and branches in addition to creating cankers on the crabapple tree. Apple scab disease appears on the leaves in the spring and then later on the fruits of the tree. Symptoms include blotches showing up and yellowing of the leaves. Fruits could get darkened corky spots, if the disease is not controlled.
Apple rust is often known as Juniper-hawthorn rust or cedar-apple rust and is a fungal disease of the crabapple tree. A symptom of this disease is rust-colored spots appearing on the underside of the leaves, causing the leaves to drop off ahead of time (defoliation). Crabapple trees with powdery mildew disease will have a powdery white substance seen on the leaves. It appears to be flour or talcum powder sprinkled on the leaves. This disease can damage the shapes and sizes of the leaves.
Buy specially grown disease-resistant crabapple tree varieties to ward off fire blight, apple scab, cedar-apple rust and other specific diseases. Do not overwater or overfertilize your tree and plant it in a location with sufficient soil conditions--not compacted soil or alkaline-rich soil. Prune as needed and keep an eye on the crabapple tree for the first signs of trouble.
Cut back and remove all of the sections of the crabapple tree disease with fire blight from the area for control of disease. Apply fungicides to control apple scab when the leaves first appear and again in a month. Control the powdery mildew disease by providing ample sunlight and proper spacing to your tree when planting. Pruning branches to improve air circulation around tree and getting rid of all diseased leaves on ground help prevent this disease also. Fungicides can also be used to treat trees afflicted with powdery mildew.