   Pine Pests: The Sequoia Pitch Moth - August 22, 2001 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Each year, between January and July, Cooperative Extension receives several phone calls regarding declining and/or dying pine trees in residential and commercial landscapes. The most common cause is improper or nonexistent irrigation (see Fall and Winter Watering, Backyard Gardener, January 3, 2001). Other factors such as insects and diseases can also increases stress on pine trees. One of north central Arizona's pine pests is the sequoia pitch moth (Synanthedon sequoiae). Although not usually harmful to a healthy tree, pitch moths can cause visible signs that cause owners distress and concern. After reading this column, you should be able to recognize and select appropriate control measures to use with landscape pines. The sequoia pitch moth is also closely related to a harmful orchard pest: the peach tree borer (see Backyard Gardener, November 10, 1999). As with many lepidopteran (moth and butterfly) pests, the pitch moth caterpillar or larva is the life stage that causes damage to plants. They rarely kill plants they attack. However, the large quantity of whitish, milky pitch gets the attention of homeowners. It appears as a raised mound of sap and sawdust on the side of the trunk often near a branch. The shear quantity of pitch causes people to assume there is severe damage occurring. Mondell (alias Quetta, Goldwater, or Afghanistan), Aleppo, Japanese black, pinyon, and ponderosa pines are all susceptible to pitch moth infestations. The adult moth flies during daylight hours and somewhat resembles a black wasp. Its wings are mostly clear with bluish black edges. It has yellow stripes on its abdomen causing it to resemble a yellow jacket wasp. Peak moth flights occur during June and July but can fall anywhere between May and September. Females lay eggs individually on and in tree bark of pine species. They prefer laying eggs near wounds or fresh pruning cuts. Eggs hatch within two weeks. Once inside, the larva feeds on the cambium layer just beneath the bark. The pinkish gray larva feeds for several months and is about ¾ inch long when mature. As the pupa matures, it pushes itself through the pitch mass until it is half exposed. A few moths may emerge from the pupa case within a year, but most will require 2 years from egg to mature moth spending the bulk of the life cycle in the larval stage. Now that you know more than you ever cared to about the pitch moth's life cycle, you are probably hoping for some control recommendations. As you have already read, the good news is that they rarely cause lasting or severe damage. However, the bad news is that they cannot be easily controlled. Due to the long life cycle, infrequent flights, and widespread use of pines in landscapes, their occurrence and location are very difficult to predict. Spraying insecticides for pitch moths is most definitely a waste of time. Cultural controls can be effective in decreasing pith moth damage. Prune pines only when necessary, and then only between October and February. This will minimize attraction and damaged areas that promote easy entry by newly hatched larvae. In addition, NEVER use line trimmers (weed eaters) around the bases of trees. Girdling caused by these machine can kill a tree in addition to attracting pitch moths. The best management strategy is to keep pine trees healthy. Irrigate them during dry periods and watch for new pitch masses. Conversely, you should be aware that pine trees could easily be over watered. Direct control is most effective. When a new pitch mass is found, you simply dig the larva out with a pocketknife (if within reach). The larva is usually just below the pitch mass and the tunnel can be followed with a piece of wire. Dig out the larva and kill it. There is generally one larva per pitch mass. Don't worry, these insects have a wealth of natural wild hosts and there is no danger of their extinction. On that note, I recently received an E-mail from an upset reader that took offense at my European brown snail control methods. The reader was especially upset by my reference to "snail stomping" and admitted to deriving pleasure from this activity. Excuse me! These are introduced species and once they are here, we'll never get rid of them. Beside that, I refuse to be a brown snail hugger. I've never eaten them either. Mind you, I would never kill a decollate snail (the type with a pointy shell). These beneficial snails are predators of the European brown snail. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 or E-mail us at mgardener@kachina.net and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://ag.arizona.edu/yavapai/anr/hort/byg/. |