Pine Needle Sheathminer
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Hosts
Lodgepole and ponderosa pines.
Distribution
Found on hosts throughout Idaho and Montana.
Damage
Larvae attack needles throughout their period of elongation and cut them off within the needle sheath. Defoliation (fig. 123) thins out branch tips.
Identification
Look for sheath-mining damage and silken webbing around needle bases from June through August (fig. 124). Faded, damaged needles can be pulled out of sheaths. Brown pupae can be found in the mass of silken webbing around needle bases in late July. After egg hatch in August, larvae bore into needles to overwinter. Larvae, when mature in late spring, are less than one-fourth inch long. Adults are small, silvery moths with a wingspan of about three-eighths inch.
Similar damages
Damage may be similar to that caused by sugar pine tortrix or pine needle casts. Sheaths mined by sheathminer, however, result in needles being easily pulled out leaving the sheath attached to the twig. Tortrix feed directly on needles, and needle casts result in shedding needles, sheath and all.
References
Anonymous. 1982. For. Insect & disease identification and management. USDA For. Serv.,Northern Region; Idaho Dept. of Lands, Insect and Disease Control; Montana Dept. of State Lands, Division of Forestry. 192 p.
Furniss, R. L., and V. M. Carolin. 1977. Western For. Insects. USDA Forest Serv., Misc. pub. 1339, 654 p., illus.
Stevens, R. E. 1961. Pine needle sheathminer. USDA For. Serv., For. Pest Leaflet 65, 4 p., illus.
Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54
