Trypodendron spp.; also Platypus, Gnathotrichus, and Xyleborus

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

Hosts. – True firs, spruce, Douglas-fir, hemlock, larch, and pines.

Distribution. – Wherever hosts are found in Idaho and Montana.

Damage. – Small diameter (one-sixteenth inch or less) holes are bored straight into tree, perpendicular to bole. Weakened, dying, or recently out or killed trees are attacked. Galleries within the sapwood cause defect in logs. Some species extend galleries into the heartwood, and freshly cut lumber may be attacked before it has dried.

Identification. – Entrance points (pinholes) (fig. 43) are marked by piles of fine, granular, white boring dust in bark crevices (fig. 44). The main entrance gallery of Trypodendron penetrates sapwood from 1 to 2 inches before branching. Tunnels with brood chambers branch in a horizontal plane and cut across the grain of the wood. Holes and galleries are surrounded by a dark brown or black fungus stain. Adult Trypodendron are stubby, one-eighth to three-sixteenths inch long, and are generally shiny and dark brown to black.

Other genera have different body shapes, gallery dimensions, gallery patterns, and life cycles.

Similar damages. – May be confused with other bark beetles; however, ambrosia beetles are the only ones which bore straight into bole producing fine, white boring dust.

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.

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