Issue: June 1, 1996

Pine pitch moth

Question: A man stopped at my house and told me I had borers in my piñon tree. He showed me that there was a lot of pitch coming from the tree. He even opened a ball of pitch and showed me the worm inside it. He told me that I had to have the tree sprayed or the borers would kill it. Did I do the right thing?

Answer: Based on the description of the worm, spraying was probably not necessary. Piñon trees are prolific producers of pitch. Pitch is used to close wounds in the bark to prevent water loss. Wind cracks caused when the tree bends and twists in the wind are sources of pitch. Insect attacks also stimulate pitch production. If an insect is involved, especially the one you probably saw, the pitch will probably have a yellowish or pinkish color. If it is due to wind or growth cracks in the bark, the pitch will first be crystal clear, drying to a frosty white, and with age turning brownish.

Some of the pitch you saw was probably due to cracks in the bark, but there was obviously an insect involved as you saw one dug from the pitch. The pine pitch moth and the pine bark moth are the likely candidates. They are not true borers and cause relatively little damage to the tree. They injure the bark a little to stimulate production of pitch. They make their home inside the pitch and feed on the pitch. Insecticides cannot penetrate the pitch and systemic insecticides do not enter the pitch; therefore, spraying is not recommended. Besides, there are not insecticides labeled for control of these insects. If the tree is heavily infested, there may be other underlying problems. An unhealthy tree is more likely to be injured than a healthy tree. Proper planting and culture are the most effective means of preventing the pitch moth or bark moth from causing major problems.

Transplanting irises

Question: Is it time to transplant my irises? How can I make more plants without hurting the plants?

Answer: Yes, August is the month to be transplanting iris and many other spring flowering perennials. They will be producing new roots shortly and will establish more readily if transplanted as new roots are forming.

When you dig them up, you can reduce them to one or a couple of "fans" of leaves with their attached stems. You don't have to leave the clumps large. In fact, they will benefit from being divided so they are not so crowded.

When you divide them, be sure to prepare the soil where they will be planted. Add organic matter, well rotted compost is preferred. This will increase the water-holding capacity of sandy soils and increase drainage of heavier soils. Use manure sparingly. Incorporate a phosphate source into the soil. "Incorporate" means don't just put it on the surface, but mix it in. According to Dr. R.D. Baker, NMSU Extension Agronomist, in our alkaline soils bone meal is often not a good phosphate source. Superphosphate will do a better job of supplying phosphorus in our soil. Colloidal and phosphate rock are allowed for certified organic gardeners.

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:, 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, or at the Desert Blooms Facebook.

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