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Royalty Crabapple Tree Disease

By Carole Ellis ; Updated September 21, 2017
Healthy royalty crab apple trees have beautiful blooms and lush foliage for much of the year.

The royalty crab apple tree is a popular landscaping tree because it is visually appealing for much of the year, thanks to various shade and hues of purple and green in its foliage. However, these trees are susceptible to several problematic diseases that can shorten their life spans. Knowing the signs and symptoms of these diseases, as well as how to treat the issue in a timely, effective fashion, will help you keep your royalty crab apple healthy and happy for years to come.

Signs of Trouble

There are some symptoms that will show up on your royalty crab apple earlier than others that will, at the very least, let you know that something is wrong. For example, if your crab apple starts to lose leaves before the end of fall, or if its leaves are stunted or discolored with spots, brown edges or blisters, that can indicate trouble. Additionally, wilted leaves when the tree is getting plenty of water can be an early sign of a problem. Withered fruit also is a bad sign, as are swollen spots on branches.

Types of Royalty Crab Apple Disease

Royalty crab apple trees are susceptible to a number of common illnesses. Blights cause the edges of the leaves to turn brown, while a number of fungal infections will give the leaves spots. Scabs, brown blisters on leaves and fruits, also are a serious problem, especially if cedar trees are also in the area. Molds and mildews create a discolored coating on leaves, fruit and even branches, while cankers are signs of bacterial or fungal infections. Wilted leaves when the tree is getting plenty of water indicates a problem with the roots and must be resolved as quickly as possible.

Time Frame

Royalty crab apple tree diseases vary in the amount of time that the tree can be infected before there is a serious problem. Blights, scabs and rusts create a cosmetic problem immediately, but the tree may live for several years after it is infected without treatment unless the accompanying defoliation is too severe for it to survive. Cankers can take five or 10 years to develop to the point where they are a life-threatening problem. Molds and mildews also tend to start out as a cosmetic issue, and only become life-threatening when they have covered too much foliage. On the other hand, root rot is a serious ailment that can kill your tree quickly -- and others in your yard along with it -- if you do not take immediate action.

Treatment and Cures for Royalty Crab Apple Diseases

If you have a problem with a rust or a leaf-spotting infection, then you can use sterile pruning to remove affected foliage and clear out plant debris from underneath the tree. In most cases, this will be sufficient, along with basic monitoring, to control the problem. However, scabs and blights will require sterile pruning to remove affected parts of the plant, but then will also need a fungicide treatment to keep the infection at bay. Consult a local arborist before treating the tree since not all fungicides or bactericides are legal in all areas of the country. Cankers will also need to be removed via sterile techniques, but they should be operated on when the weather is cool to prevent the spread of disease. Finally, root rot must be dealt with immediately, usually by fumigating the soil, limiting the amount of water that the tree gets to give the roots a chance to recover while the rot starves, and by isolating your tree, as much as possible from other trees.


The best way to keep your royalty crab apple healthy is through constant vigilance. Always be on the lookout for trouble signs and careful to remove problem branches and leaves immediately. Water using a drip hose early in the morning, being careful not to get the leaves of the tree wet. Water only when absolutely necessary, since most royalty crab apple trees can resist drought once they are mature.