Western Pine Shoot Borer

Eucosma sonomana Kearfott

From: Field Guide to Diseases and Insect Pests of Idaho and Montana Forests, USDA Forest Service Northern Region, Publication Number R1-89-54

Hosts. – Ponderosa and lodgepole pines.

Distribution. – On hosts throughout Idaho and Montana.

Damage. – Larval mining in the terminal shoots impairs or stops shoot and needle elongation and can affect development of new buds. Repeated attacks reduce tree height and may cause deformed crowns.

Identification. – This moth does not leave feeding scars, webbing, or frass on the surface of infested shoots. About May, larvae enter leaders near terminal buds and mine downward in the pith. Circular exit holes from the pith in midsummer are evidence of borers. Terminal shoots become thickened, do not wilt, and their needles usually remain green but have a stunted "shaving brush' appearance (fig. 92). Sometimes terminal and lateral shoots are killed and turn orange-red. The mined pith is tightly packed with frass but the xylem and phloem are not damaged (fig. 93).

Similar damages. – No other pest produces the shortened, compacted appearance of affected terminals, without killing, as does the western pine shoot borer. Lateral shoots also may be killed by Diplodia, comandra, or other canker diseases. Look for evidence of shoot borer mining in the pith.

Link to Images in Forestry Images

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., and D. T. Jennings.  1977. Western pine shoot borer: A threat to intensive management of ponderosa pine in the Rocky Mountain area and southwest. USDA For. Serv., Rocky Mtn. Forest & Range Expt. Sta., Fort Collins, CO, Gen. Tech. Rpt. RM-45, 8 p., illus.

[  Back  ]