Larvae of various bark moths, or coneworms (Tortricidae), bore in cedars, cypress, and false cypress (Chamaecyparis, Cryptomeria, Cupressus, and Thuja spp.) and other conifers. Infestations are especially common in Monterey cypress (Cupressus macrocarpa) in coastal California.
Identification
Cones with holes, brown to red frass (excrement), and silk webbing characterize an infestation of coneworms (the larvae of bark moths). Cypress may become so severely infested that the frass, which is held loosely together by larval webbing, appears to drip from the cone clusters.
On Monterey cypress, larvae of C. cupressana and E. hopkinsana are found under the bark, in cones, and occasionally on foliage; only an expert can distinguish the species. Epinotia hopkinsana mostly infests pines. Cydia cupressana is the more common species in Monterey cypress.
Cydia cupressana larvae are gray to white, have a brown head, and grow up to 1/2 inch long. The adult is a dark brown moth with transverse silver and gray bands on the forewings and a wingspan of about 1/2 inch. The eggs appear as small, ovoid discs and occur singly on cones and limbs.
Life cycle
In relatively undisturbed, natural stands of Monterey cypress in coastal areas, the larvae feed almost exclusively in cones and are innocuous. However, in urban areas where soils are fertilized and irrigated, cypress grow more rapidly especially when young; this accelerated growth results in unnaturally thin outer bark where the female moths are attracted to lay eggs.
Larvae tunnel and feed under bark in urban areas during most anytime of the year. Inside the cones, the larvae feed mostly on the scale tissue. They feed on the seeds in spring when the immature cones are small and succulent.
Cydia cupressana has two generations per year, and overwinters as larvae and pupae. In coastal areas, larvae feed continually during the winter, and in January begin to pupate. Adult females, emerge, mate, and lay eggs beginning in March. Larvae hatch, feed, and increase in size from March through August. By late August, the mature first-generation larvae begin to pupate into adults.
Larvae of the second generation appear beginning in September. These larvae and many of the later-developing, first-generation (spring) larvae will overwinter. There is much overlap between the spring and fall generations. Adults and eggs can be present anytime from March to November.
Damage
Feeding by the larvae can kill branches, which sometimes die back to the trunk. Coarse boring dust is seen on cones, trunk wounds, and branch crotches. Larvae often colonize Cypress Bark Moth on Monterey Cypress.
