Fir Engraver

Scolytus ventralis LeConte

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

Hosts. – Primarily grand fir. Occasionally it will infest Douglas-fir, subalpine fir, western hemlock, and spruce.

Distribution. – Throughout host range.

Damage. – Adults and larvae feed in phloem layer of inner bark. Frequently only "patch" attacks are made on bole. Often trees are top killed. Trees can be killed if attacked by enough beetles (fig. 53). Trees of any size may be attacked.

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Figure 53 - Top kill and tree mortality caused by Fir Engraver.	Figure 54 - Egg and larval gallery pattern of Fir Engraver.
Identification. – The gallery pattern of the fir engraver is unique (fig. 54). Unlike most other bark beetles, the female constructs a horizontal egg gallery, perpendicular to the grain of the wood. Red-brown boring dust marks the sites of new attacks during summer months. Eggs are deposited on each side of the gallery and larvae tunnel at right angles to the egg gallery paralleling the wood grain. Larvae are present from midsummer until the next June. Adult beetles are shiny, black, and about one-eighth inch in length. A side view shows that the end of an adult's abdomen is incurved (fig. 52).	Image Unavailable
	Figure 52 - Comparison of body shapes of four common genera of bark beetles.

Similar damages. – Secondary bark beetles attacking grand fir may be mistaken for the fir engraver, but distinct gallery pattern and beetle shape distinguishes it from associates. Root disease is often a precursor.

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. 1971. Fir engraver. USDA For. Serv., For. Pest Leaflet 13, 7 p., illus.

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