Garden Detective

What’s wrong with her redbud?

What’s wrong with this redbud? The leaves became mottled and started dropping in summer. The cause may be found at the tree’s roots.
What’s wrong with this redbud? The leaves became mottled and started dropping in summer. The cause may be found at the tree’s roots.

We planted an Eastern redbud tree in our backyard several years ago. Last year, I noticed that in late summer the leaves started getting mottled, yellowing and dropping. Bark was missing as well, but we blamed that on a toddler.

This spring, it looked quite healthy and didn’t even get much of a caterpillar infestation like it used to. However, as summer wore on, much more bark came off and no one was doing it. Plus the leaf discoloration and dropping became severe. I think all of the leaves that have dropped have been from disease and not seasonal change. What should I do for the tree?

Mary Lowe, Roseville

According to UC master gardener Mary Griggs, there are several possibilities for the problem with your tree, including root and crown rots and verticillium wilt, a soil-dwelling fungus that infects through roots, caused by pathogens promoted by excess soil moisture and poor drainage. Both result in leaves that fade, yellow, brown or wilt. Both may result in eventual death of your tree.

First, let’s look at verticillium wilt. In some, but not all plants, peeling back the bark on newly infected branches may reveal dark streaks following the wood grain.

Many tree varieties are susceptible to this disease including redbud. Other trees that can be hit hard by verticillium wilt are maple, catalpa, persimmon, ash, golden rain, olive, pistache, elm, tulip tree, Southern magnolia and the whole Prunus family of fruit and nut trees – plum, apricot, peach, cherry and almond.

This disease also attacks many vegetable crops especially tomatoes, potatoes, cucumbers, pumpkins and melons.

Verticillium wilt may be managed by providing good cultural care for your tree. Provide proper irrigation, modest amounts of slow-release fertilizer and other appropriate care to promote new growth and increase chances of survival. If it becomes necessary to remove the tree, replace it with a plant that is resistant to verticillium wilt.

Among those trees that are very resistant or immune to verticillium wilt are birch, eucalyptus, dogwood, oak, willow, liquidambar, walnut, locust, mulberry, apple and most citrus species.

Root rot and crown rot are caused by Phytophthora cinnamomi and several other phytophthora species that commonly infect the roots and crowns of landscape plants. This mold can continue up the tree and may be the cause of your peeling bark.

Both these issues can be prevented – or at least minimized – when choosing and planting a tree in your landscape.

When planting a tree, the site should be prepared beforehand to provide appropriate conditions. Improve drainage at the site and only plant species that are not susceptible to phytophthora or verticillium wilt. It may help to plant your tree in a mound to facilitate drainage.

The bark issue is mostly likely connected to leaf drop. However, anthracnose will also cause premature leaf drop. Fruit tree leafroller will cause defoliation, too.

For a more specific diagnosis, have a trained arborist inspect your tree.

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