Issue: August 5, 2000

• Browning pine trees
• Yucca

Browning pine trees

I live in the Cedar Crest area. There are a lot of pine trees with brown needles in my area. What is the problem and what can we do to protect our trees?

There are a number of problems that are causing brown pine needles this year. The winter drought is one contributor. Winter stress can result in brown needles in the summer. Stressed trees may also be attractive to pine bark beetle which may also cause browning of pine trees.

Bob Cain, NMSU Extension Forest Entomologist, has identified pine needle miners in some areas of New Mexico. This is also a cause of browning pine trees in New Mexico this year.

There are two species of needle miners that may infest either ponderosa or pinyon pines. These species differ in their life cycle, but their effects are similar. They cause browning of the needles, early needle drop, reduced growth, and in some cases death of the trees.

To determine if specific trees have needle miner infestation, look closely at the needles for small holes where the needle miners have emerged. You can also split the needle lengthwise looking for the tunneling through the center of the needle caused by the miner. If the infestation is not too severe, the tree should recover on its own without treatment.

If the infestation is severe, use a foliar systemic insecticide while the miners are still active within the needle.

Additional information regarding the above is available in the publication, "Conifer Pests in New Mexico," which is available from the Cooperative Extension Service, State Forestry Office, and the U.S. Forest Service in New Mexico.

Bob Cain has also identified some fungal needle cast in localized pockets. This is probably due to weather conditions and very localized. This problem should naturally improve as weather conditions change and should not be a major cause for concern. Fungal needle cast along with winter drought is probably the most likely cause of browning of pine trees in the Cedar Crest area.

Yucca

I have a question about yucca trees. I live in the northeast section of Albuquerque at an altitude of about 6200 feet. My wife recently bought two yucca trees for the back yard similar to the ones I see all over the desert floor in the Alamogordo area. However, there's nothing like that growing naturally near me. Since we moved out from Boston less than a year ago, we don't have a lot of experience with yucca care and feeding, and I can't find anything on the web or in the library that covers the topic. (Lots of talk about what they look like and where they come from, but nothing on "here's how you take care of one at home".)

Can you point me to care information or to a person who is likely to be able to tell me about it?

There are many yuccas which may be cultivated. Not all do as well in a given location as others. The one often desired in landscapes is sold as the "palm yucca." This has broad leaves and is best adapted to southern New Mexico, though it will grow further north. The soaptree yucca has narrower leaves and is better adapted into the central part of New Mexico. By virtue of its better adaptation, it is less likely to receive winter injury and is more resistant to certain insect pests. There are even some yuccas which grow north into Montana, though these are not "tree" form yuccas.

There is relatively little printed information regarding yucca cultivation because they are often considered very easy to grow (if the better adapted species are planted), and because there are relatively few garden books printed for the arid west, especially our area. There are a few books. You might wish to check for them in your local library or book store. Of course, your local Cooperative Extension Service office is a source of free information adapted to your area as are many of the local nurseries.

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.

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

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