With more than 1000 varieties, the crabapple tree is one of the most showy and commonly planted trees in the U.S. The crabapple tree is an adaptable one, quickly adjusting to various types of soils, pH levels and irrigation variations. Providing a continuous visual impact, this tree displays colorful swelling buds in the early spring, showy flowers from spring through summer, richly colored foliage and vibrant fruits in the summer through fall and harvest fruiting in the winter months. The crabapple tree is susceptible to several fungal and bacterial diseases which can stunt its vigorous growth and vibrancy.
Powdery mildew is a common fungal disease that begins as a cosmetic infection to the tree's foliage. The disease is transported by fungal spores which infect newly developed and young foliage. Diseased foliage will initially display small, white to gray colored specks on the surfaces. Progression of the disease will cause an accumulation of fungal specks which will appear as a white, powdery covering on the surface of the leaves. Leaves may also curl and wilt from the infection. Stems, flowers and fruit may also experience symptoms which include growth stunt, wilting, browning and drying of flowers and fruit, weakened stems and defoliation. Wash away mildew on newly to moderately infected trees with a vigorous water flow. Prune away severely infected areas with sterile shears. Treat severely infected crabapple trees with a fungicidal spray designed for fungal mildew.
Fire blight is a destructive bacterial disease that can cause fatal results to the crabapple tree if left untreated. Infected crabapples will initially display tan-colored bacterial ooze running from the points of infection. Targeted infected areas include woody areas, flowers and fruit. The ooze dries into dark-colored streaks and cankers will begin to develop, usually around the base of the trunk. Infected flowers will wilt and die and are usually infected first. Crabapple fruit will grow in a distorted manner, turn brown and die. The bacterium of fire blight lies dormant in fallen debris and mummified fruit that remains during the winter months. The potential for infection is greatly reduced by keeping the crabapple tree's canopy and surrounding areas free of debris and removing all fruit from the tree by the final harvest. Prune infected areas from the tree. Copper-based fungicidal sprays are effective in reducing the potential for infection.
Cedar Apple Rust
Cedar apple rust is a common crabapple disease that is caused by several types of fungus. This fungus lies dormant during the winter months on the crabapple tree. In the spring months, the fungus is transported by fungal spores onto the newly developing foliage, stems and fruit. Infected areas will develop swollen growths and lesions which take on a yellowish-orange color. Infected foliage will also develop yellow-colored spots with fruiting fungal bodies. Fungicidal sprays that include sulphur or copper are effective in managing the disease. Prune infected areas from the tree.