Pest description and damage There are nine Argyresthia species that attack different conifers (pine, hemlock, etc.) in the Pacific Northwest. One of them, the adult cypress tip moth (cypress tip miner) is common enough to merit attention in many books. The moth is silver-tan and approximately 0.13 inch long. The larvae are green, about 0.13 inch long. The larvae tunnel in the growing points of the 1- and 2-year-old shoot tips. The cocoon is a white, somewhat papery structure made in dead or living foliage. Damage typically is limited to the tips of twigs. The exit holes are dark and may resemble symptoms of Didymacella leaf blight, a fungal disease. Foliage does not discolor in the affected areas until late winter. After this, the brown, dead twigs break off readily. Cultivars of Juniperus chinensis, J. virginiana, and J. sabina also are affected. The entire plant can appear brown in a severe infestation, and repeated infestations cause dieback. Failure to gain control may require taxonomic identification to ensure the right species is identified. Juniper can recover from extensive feeding damage from these moth larvae.
Biology and life history Adult moths appear on plants around May-June. Eggs are laid on the shoot tips of host plants. The larvae tunnel under the leaf scale and feed in the foliage until the following spring. Larvae leave the mines in spring and spin a white cocoon in which they pupate. After several weeks, the adult moths emerge. There is one generation per year.
Pest monitoring Watch for larvae ballooning from the plant on a silk thread or moths flying around the plants. A sticky coated plate hung horizontally provides easy means of monitoring for small "worms" when they exit.
Resistant cultivars are available.
For more information
Antonelli, A.L. and C.R. Foss. 2003. Cypress Tip Moth. WSU - Puyallup. PLS-60 (http://www.puyallup.wsu.edu/plantclinic/resources/pdf/pls60cypresstipmot...)
Rosetta, R. 2008. Cypress tip moth. PNW Nursery IPM (http://oregonstate.edu/dept/nurspest/cypress_tip_moth.htm)