1 - Environmental stress can make trees more susceptible to insect attack.

Yard and Garden May 25, 2013

Q.

The Italian cypress trees along the side of my yard have died at the top. I noticed that there are other cypress trees with the same symptoms. What is happening? What can I do to save the trees?

A.

There are probably several factors working together to cause this problem. It is not uncommon to see the Italian cypress trees with dead or dying tops, especially after periods of environmental tress. There are some insects that have caused this problem in the past and they are probably active again. The cold winters, especially the one a couple of years ago, have injured the trees. This injury makes them more susceptible to insect attack. The dry summer last year and our recent dry winter have also created an environment favorable to the insects. Proper irrigation from the dripline (very close to the trunk in the case of Italian cypress) outward many feet from the trunk is needed to provide water to the wide-spreading absorbing roots. Irrigate to moisten the soil to a depth of two to three feet each time you irrigate. This provides a consistent environment for root health and activity. During the growing season you should irrigate twice a month and during the dormant season water at least once a month unless there is adequate precipitation to moisten the soil to maintain that two to three foot root zone. Fertilizer is not required at this time. Once the health of the trees returns, light fertilization can be resumed.

You may need to consider treating any insects that have taken advantage of the stressed trees. Cypress bark beetle and cypress scale are insects that can cause the damage you described at the top of your trees. Your local NMSU County Cooperative Extension Service agent can help you determine if insects are causing the dieback and which insects are involved. They can also advise you as to appropriate treatment measures to manage these insects to save your trees.

Irrigation may be all that is required, but it will not hurt to have the Extension Service agent confirm that there are no other problems.

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.

Links:

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

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