Ask the Plant and Pest Professor: Maple Trees, Carpenter Ants, and Root Damange


Question #1: We have two maple trees in our front yard. The roots are at the surface and my husband has to run over them with the tractor when he mows the lawn. He wants to cut them out but I think that will hurt the tree. Who is right?

Answer #2: Removing tree roots is not recommended as this could potentially damage or even kill a tree. However, running them over with a lawn tractor is also not good for the tree. People will sometimes add soil to cover the roots and plant more grass seed. This is not the best solution either as the roots will just rise to the surface again and it is not recommended to cover roots with more than 2 inches of soil. The best solution is to replace the grass with a low-maintenance, low growing groundcover or a 1-2 inch layer of mulch. Just make sure the mulch is not packed up around the base of the trunk. Leave about a 2-3 inch barrier of soil.

Question #2: How concerned should I be about carpenter ants? I am assuming that is what I am seeing as sometimes I find one or two large black ants inside my home. Does that mean I have a nest inside?

Answer #2: Carpenter ants usually nest outside in wo

od piles, rotting trees or other sites with older or rotten wood. It is very common to find some in the house on occasion especially in the spring as workers travel from the nest to find food. Occasionally, they will nest inside if there is a moisture problem and a suitable site exists. Look for sawdust-like material called frass near moisture damaged wood. If there is a nest indoors, in addition to treating it, you need to figure out and correct the moisture problem. Any wood that is compromised by moisture should be replaced. For additional information see publication HG 115 Carpenter Ants found on our website.

Question #3: I have a rhododendron planted in one of my ornamental beds that is not looking good. Within the last 2-3 weeks I have noticed that the leaves are very droopy, some of them are turning brown and hanging on the shrub. It almost looks like it needs water but I know it is not that because we have had so much rain. Not sure what to do. Can you help?

Answer #3: Has anything like drainage, new construction or any root disturbance occurred around the shrub? Root damage can cause the wilting you describe. There is also a little creature called a vole that chews on bark at ground level causing major branches to die. Another possibility is Phytophthora root rot. This soil pathogen exists in soil but is worse where the soil is wet and drainage is poor. Some plants like rhododendrons are more susceptible to this pathogen than others. Unfortunately there is no control and your shrub will most likely succumb. Do not replant another rhododendron or azalea in this spot. Chinese and winterberry hollies, Abelia, and Calycanthus are some suggested replacements.

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