April 12, 2014

1 - Sometimes a horizontal fence is needed to protect a garden from gophers and rabbits.

Yard and Garden April 12, 2014


I have a mulberry tree that I think is in big trouble. The bark has peeled off of the whole side of the tree facing the sun. I have put a blanket around it, thinking it might be sunburn...but when I did that, I noticed hundreds of perfectly round holes that go almost all the way down the tree. I do not want to lose the tree, but am worried it is infested with something?


Mulberry trees are very resilient, so there is hope, but there will probably be damage to the tree. The degree of damage and the potential for hope of survival may depend on the size/age of the tree. If the damage was not too severe there may be enough healthy tissue on the opposite side of the trunk to support wound closure and growth of the tree. However, injury has occurred and allowed entry of decay organisms that may result in the failure of the trunk in the future. The location of the tree with regard to structures or places frequented by people (tables, chairs, etc.) will be an important consideration in deciding whether to keep the tree and allow it to recover, or to remove and replace the tree.

If this is a young tree with a trunk diameter less than 6 inches or so, your first guess as to the cause, sunburn injury to the trunk, may be correct. The borers you described would be secondary invaders taking advantage of the damaged portion of the tree. Borers tend to attack dead or dying tissues. If the other side of the trunk is uninjured, as is often the case with sunburn injury, then there is still healthy tissue on that side of the tree. These healthy tissues will contain the xylem that carries water and nutrients to the top of the tree to support photosynthesis in the leaves. There will also be healthy phloem to carry food produced in the leaves to the roots. If there is sufficient healthy tissue, the wound should begin to close and the tree may survive.

If this is an older tree the borers may have come before the bark damage. This would indicate other stresses such as drought or winter injury had initiated the problem. Once again wood borers would be secondary problems. Since the borers have matured and emerged, leaving behind the holes, they were probably there last year. They have emerged and flown away, perhaps depositing additional eggs in this or nearby trees. If the trees are well cared for, and if there is enough healthy tissue on the other side of the trunk as described above, the tree may overcome the problem. However, as described above, damage has occurred and in time the trunk may fail (break) causing damage to nearby structures. Consider the location of the tree if you choose to let the tree remain.

An onsite examination of the tree by your local NMSU County Extension Service agent or a certified arborist will help determine the true extent of the damage, the exact cause, and the best course of action for the future.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.


For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!