Issue: June 17
There are several potential causes for a tree to appear to die suddenly
Q. I have an apple tree that blossomed seemingly normally this year. We went out of town on vacation and came back to a dying apple tree. We did have substantial May precipitation compared to what we are used to here in western New Mexico. I think the tree died sometime in the latter half of May while we were gone.
When we returned from vacation, the bark had turned an orange color and the tree did not produce leaves. It seemed to be drying-up and dying. Other apples trees in the area did not exhibit this same phenomenon.
There are suckers coming from the shallow horizontal roots and they are doing quite well. Will the suckers grow to be productive fruit-bearing trees?
A. There are several things that could have caused the sudden death of the upper portion of your tree, but I do not have enough information to say what did it. Here are some possibilities and things to look for to determine the cause:
A lightning strike can kill a tree. It may or may not leave visible damage on the trunk (split bark, charring, etc.)
A late freeze (this happened in much of New Mexico this year) can cause damage, especially if the tree is in a low lying area where cold air will accumulate when surrounding trees are not injured. This may not kill the tree, but it may have killed buds on the twigs. Remaining buds may begin growth later in the summer. The discoloration of the bark on the tree suggests that this is not the problem and renewed growth is unlikely.
Anything that girdled the trunk of the tree (rabbit or other animal eating the bark at the base of the tree, insects boring just under the bark of the tree) may be the problem. The xylem deeper inside the trunk may have been undamaged and able to send water upward so that the tree flowered, but the phloem and cambium just under the bark may have been injured, so after the tree started to bloom, it depleted stored food reserves and died. If you suspect girdling insects, evidence to look for would be emergence holes and tunneling galleries just underneath bark that peels off easily.
Gophers can injure trees by consuming the roots of the tree without leaving visible evidence on the above ground portions of the tree. Signs of gophers in the area (mounds) would be an indication that this may have been the problem.
Fireblight (a bacterial disease) spread by honeybees pollinating the tree could cause dieback. The tree does not usually exhibit complete dieback, but as you said it was wetter than usual and that could have made the damage greater. If you think it is this, send a sample to the NMSU Plant Disease Diagnostic Lab through your local NMSU Extension County Agent.
Do any of these seem to be likely causes?
The suckers you mentioned sprouting from the roots (not consumed by gophers if they were the problem) will be a rootstock variety or seedling and may not produce the desired variety of apples. If there is no systemic disease, the sprouts can grow and replace the tree. A desired variety can be grafted onto the sprouts to produce more desirable fruit.
For more gardening information, visit the NMSU Extension publications World Wide Web site at http://aces.nmsu.edu/pubs/_h.
Send your gardening questions to:
Yard and Garden, Attn: Dr. Curtis Smith
NMSU Agricultural Science Center
1036 Miller Rd. SW
Los Lunas, NM 87031
Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist with New Mexico State University's Cooperative Extension Service. NMSU and the U.S. Department of Agriculture cooperating.