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Hypoxylon canker is a fungal disease in trees that can become a problem in droughts. - Original Credit: For The Baltimore Sun
Hypoxylon canker is a fungal disease in trees that can become a problem in droughts. - Original Credit: For The Baltimore Sun (Handout / HANDOUT)

Several of my trees have these black spots on the trunk. Is it a problem?

This appears to be hypoxylon canker, a fungal disease. It is often present in trees but doesn’t become a problem until a tree is severely stressed, primarily by drought.

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The tree canopy (top) may show dieback first (though many things can cause this symptom.) The outer bark sloughs off where the fungus is underneath. At first the fungus appears brown, then gray or silver, eventually black. There is no cure, though an infected branch can be pruned off and moved off-site. Preventing stress is key to preventing infection.

Keep your trees healthy by:

<<Watering 1” a week during serious drought;

<<Protecting trees from construction, soil compaction over roots, and root damage;

<<When mulching around the tree, do so 2 to 3 inches deep but DO NOT pile mulch against the trunk;

<<Avoid applying weed killers on trunks or under trees — especially herbicides which travel down in the soil to kill roots.

A car skidded on ice and ended up in my front yard, but not before it rolled over my bushes. Can my bushes be salvaged if I clear away the broken parts? I’m not sure what kind of shrub it is — evergreen leaves (not needles) and bright yellow inside where the bark is broken. Will they be able to recover, even though this happened in the winter?

Good news and bad news. The good news is that for most shrubs you can prune out the damaged areas, as low as 6″ off the ground. This will stimulate new growth in the spring. However, it may take years to fill in.

The bad news is that your shrub description sounds like barberry, an invasive shrub now known to encourage deer ticks and higher rates of ones infected with Lyme disease. So this as an opportunity to plant new kinds of shrubs. Natives with flowers and/or berries for wildlife are best. More good news.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.

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