Issue: May 5, 2002

Pitch moth

I have a relatively large pinyon tree that appears to be infested with either the pine pitch moth or pine borers. In digging around in the cloudy, pink pitch, I've found insects that resemble worms or larvae. The tree's health seems to have declined over the past few years. Your past comments regarding the pitch moth larvae indicate that it's not particularly harmful to the tree. How can I tell the difference between the pitch moth larvae and borers? John H. Albuquerque

Your description of pitch moth or bark moth larva is good. These are not true borers because they only bore into the bark, not the wood. Their purpose is to cause the tree to produce pitch, as you see your tree doing. Borers will feed in the cambium and phloem tissues under the bark doing much greater damage than the pitch moth larvae which feed on pitch. The borers will not be found in the pitch nodules, but the nodule of pitch is the place in which you will find the pitch or bark moth larvae. The pitch provides both a "home" and supply of food to these larvae. Unless the attacks are numerous and repeated, the pitch and bark moth larvae do minimal damage to the trees. Smaller trees are more severely affected, as are trees that are under stress. In our current drought, there are numerous trees suffering from stress. Good tree maintenance, proper irrigation, and pruning are the best means of protecting the tree. There are no insecticides labeled for control of these pests. As you have pointed out, the damage is not a great concern in a healthy tree. You can carefully remove the insects manually by digging into the pitch nodule, but don't increase the damage by cutting into the bark. Heavily infested branches may be removed if that will not damage the form of the tree, but it is rarely necessary to prune the infested branches from the tree.

Coffee grounds in terrarium

What are the reasons I would want to put coffee in my plants? I read an explanation but I was told it was more than just a way to add acid to the soil so that some plants will grow better. I am taking an earth science class right now in college. We are getting ready to make a terrarium. Is it a good idea to put a small amount of coffee in there?

The coffee grounds will indeed acidify the soil, as will other organic matter. If the plants you will be using require acid soil, coffee grounds or a compost/peat based soil will be beneficial. The addition of organic matter to mineral soils is helpful because the decomposing organic matter slowly releases nutrients into the soil, increases the water-holding capacity of sandy soils, and improves the structure of clay soils. Plants grown in terraria, if native to tropical rain forests, will be best adapted to soils containing much organic matter. If the terrarium plants are native to arid soils, the organic matter may not be beneficial. An answer to a similar question may be found in the Yard and Garden archives at the NMSU College of Agricultural, Consumer and Environmental Sciences web site at http://cahe.nmsu.edu/ces/yard/2000/111800.html and http://cahe.nmsu.edu/ces/yard/2001/120801.html. In the first of these web pages, the answer provides some cautions regarding use of coffee grounds in flower pots. The second discusses coffee and other beverages used to irrigate plants.

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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