1 - Stress from a previous year may have led to insect infestations that kill trees.

Yard and Garden
May 5, 2012

Q. #1 : I have a large cypress tree in my yard. I live in Las Cruces. The top third is completely brown with brown and green mixed in the bottom two-thirds. I have been watering it about twice a week for the last month or two. I also put Miracle Gro tree spikes around the tree in the fall. Do you have any suggestions how I can help my tree?

Suzy
Las Cruces

Q. #2 : I have a Thuja ‘Green Giant’ about 5 feet tall that I planted last fall - I was careful to water it and we had quite a bit of snow at my house, but now it is almost dead. There is only one live branch at the very base; the rest is all bleached and crispy. Will the top "come back" if I leave it alone? Should I cut off the dead part, if I do will it grow up again? Should I wait for the next Green Waste Week and put it out of its misery? I have a similar problem with a purple-leaf plum I planted last spring. Its trunk is about 1.5" diameter at the bottom, it is about seven feet tall if you count the dead part. Its top dried up during last summer's heat/dry wave (although I watered it twice a week). I was hoping it would come back, now I have one little branch budding out about two feet off the ground. Same questions as the Arborvitae - should I cut off the top? The bark up there feels a little wrinkly now, I am guessing because the wood underneath is dead.

Jane H.

A.:

Although these questions are about different species of coniferous trees and a deciduous fruit tree and are from different parts of New Mexico (the reference to snow suggests that), the answers will be similar and relevant to people in most parts of our diverse state.

It is impossible to state with certainty the cause of the problems, but it is possible to make statements as to some probable causes. I also suggest that you contact your local NMSU County Extension Agent for confirmation after you have read my suggestions.

Older conifers may still be declining from the winter of 2011. Injury suffered from that extreme cold could have predisposed the trees to several insects. Cypress scale was a problem several years ago and may have increased in infestation levels due to winter damage. Several species of borers will also increase their infestation levels when numerous injured trees become available to them. The winter of 2011 provided the stressed trees. These trees may have seemed to survive the cold, but may yet succumb to insect attack. Your NMSU Extension County Agent can help you determine if this is the case.

The newly planted trees that exhibited injury last summer may also be attractive to insects. Look for signs of boring insects at the base of the damaged portion of the tree. Both coniferous and deciduous trees have boring insect pests that may be responsible.

Excessive watering can also cause stress that will attract damaging insects. The soil surface will dry much more quickly than deeper soil where the roots are trying to grow. If there is too much water for a prolonged period of time (summer or winter), the roots will suffocate and die. The appearance will be as if there was not enough water because the dead roots cannot absorb water. The soil around trees should be moist to a depth of 2 to 3 feet and the surface 3 to 6 inches of soil allowed to become dry between irrigations. With older trees this water should be applied under the drip line of the tree and outward. Newly planted trees should be watered around the base of the tree for the first one to two years, then away from the trunk as the roots extend outward into the surrounding soil.

In the case of all the trees described in your questions, it sounds like your best option is removal of the tree and replacement. However, before removing the tree contact your County Agent and determine the cause of the problems so it can be avoided in 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.

Links:

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!