Sequioa Pitch Moth

Order: Lepidoptera
Family: Sesiidae
Species: Synanthedon sequoiae

Description & Life History:

It’s time to start picking out that perfect Christmas tree. During November and December, we have a history of people bringing in sappy samples from their poor tree that was slated to stand high in the living room. This is the time of year that people notice the symptoms of the sequoia pitch moth.
The sequoia pitch moth (SPM) is a pest of ornamental conifers and forests. SPM feeds on pines (Pinus), Douglas fir (Pseudotsunga) and spruce (Picea) but does not actually infest sequoia trees. So, why is it called the sequoia pitch moth? I don’t know.

The adult SPM is a clearwinged moth that mimics yellowjacket wasps, much like many other clearwing moth species. Adult moths are ¾ inch long with yellow and black-banded bodies. The wings are outlined in dark blue scales with yellow scales near the base of the wings. Adults fly during the day from May through August. The peak flight tends to happen in June. Adult females lay eggs singly near wounds or openings on the tree trunk or larger branches. Eggs hatch within 2-3 weeks. Larvae bore into the bark and begin to feed on the inner bark tissue and outer sapwood. Feeding from the sequoia pitch moth causes large pitch masses to form. Larvae can take up to two years to develop. Mature larvae are 1 inch long and are dirty white, pink or yellowish in color with dark head capsules. Once larvae mature, pupae are found protruding from the pitch mass.

Damage:

SPM causes unsightly pitch masses on susceptible trees. Extensive infestations can cause dieback of the tree’s canopy, girdling and death of the tree. Infestations can weaken the tree’s structure and can cause breakage of limbs and trunks. SPM prefers trees over five feet high but can infest young saplings. SPM, like many tree-infesting pests, prefer weakened trees with mechanical injuries. SPM damage can also open opportunities for other pests to invade such as bark beetles, rusts and cankers. Damage can be confused with other pests, like the pine pitch canker.

Monitoring

Regularly inspect trees for pitch masses. Older pitch masses will have gray colored, hard pitch while fresh, active masses will be soft, tacky to the touch and milky pink or orange in color. A pheromone lure is available for purchase to monitor the flight activity of the adult moths.

Management

Sequoia pitch moths rarely kill trees. In nature, most trees will have SPM but only in very small numbers. Plant pest-resistant trees. The most excellent MG reference, “Insects that feed on trees and shrubs” has a long list of resistant and susceptible pines.

Tree health is key for warding off these annoying pitch pests. I’ve visited a Douglas fir tree farm to look at some sick trees. The farmer showed me the many pitch masses on his trees but, what caught my eye was the numerous wounds made by a weed-whacker. It was obvious that SPMs were exploiting these injured trees. Reduce any mechanical damage, including pruning cuts, to growing, susceptible trees. Do not leave tree stakes attached for too long. Rubbing wounds caused by tree stakes can cause more sites for SPM to infest.

Maintain tree health. Be sure that your trees are matched to the right habitat. Be sure to meet all the tree’s nutrients and water requirements. It is important to keep the tree healthy.

Prune off infested branches during October through February. Make a clean pruning cut and leave the tree collar intact so the tree can heal before more moths fly in May. If pitch masses are easily reached, dig out the larvae during the winter and spring. Using a pocketknife, or like tool, pry off the pitch mass. Physically destroy or remove the larvae when you encounter them. There will be only one larva per individual pitch mass. Leave the wound clean and remove any other debris. Pruning paint is not necessary and may slow or disturb the healing of the wound.

There are no pesticides available to recommend for treating SPM problems. Recent work using a management technique called “mating-disruption” shows some promise for reducing SPM populations in a backyard or tree farm setting. If trees are baited with multiple pheromone dispensers, males will have a difficult time finding female moths to mate. Using this technique will require multiple years of disruption because sequoia pitch moths take up to two years to develop. This method of management has proven to be very useful for controlling other pests over large areas, such as codling moths and gypsy moths. Populations can decrease rapidly in a single pest generation, leaving many confused, frustrated male moths and more unmated female moths. What other evil, torturous pest management methods will entomologists think of next?

Image 1. Adult sequoia pitch moth.

Image 2. Pupal case protruding from pitch mass.