Issue: July 19, 2003

Sap on trunk of cypress tree

There is a lot of sap bleeding out of the trunk of my Leland cypress tree. What is wrong with the tree?

An insect called the cypress bark beetle attacks cypress and juniper trees. The first evidence of the insects attack is flagging of the branch ends. When the branch flags, the branch breaks several inches from the end where it has been fed upon by the beetle, weakening the branch. The end of the branch then turns brown. As the level of infestation increases, the insects begin to attack the trunk of the tree. The sap on the trunk may be evidence that the trunk is under attack. After the adult insects bore into the trunk and lay eggs, the young larvae hatch from the eggs and begin feeding on the phloem and cambium tissues just under the bark. This girdles the tree, interrupting the flow of sugars from the leaves to the roots. After a time the roots die from lack of food. They stop sending water and minerals to the leaves that then appear to die suddenly. As the top dies, the larvae pupate and metamorphose into adult beetles. These adults emerge from the tree trunk, leaving obvious exit holes. By this time, it is too late to do anything. In the earlier stages of attack, when the damage is evident on the flagging twigs and perhaps early in the time when pitch is evident on the trunk, care of the tree by proper watering may enable the tree to resist the bark beetle attack. Once the leaves have exhibited a dull green color, indicating that they are dying, it is too late. Removal of the tree is the best option. However, do not allow the cut tree to remain on the property. If it remains, the beetles will emerge and attack nearby susceptible trees. You may have to decide which trees are important enough to your landscape to warrant extra irrigation during these times of drought. Other trees may remain until you see evidence that they are infected and must be removed. We will not be able to save all the trees. There are no chemicals registered for control of the cypress bark beetle, so chemical control is not an option. If you want to learn more about this potential pest, go to the excellent information at the University of Arizona web site: http://cals. arizona.edu/pubs/insects/az1316.pdf

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 and the NMSU Horticulture Publications page.

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