Defoliating Weevils

Magdalis gentilis LeConte and Scythropus elegans (Couper)

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

Hosts. – Lodgepole pine and ponderosa pine. May feed on other species of pines and Douglas-fir.

Distribution. – Probably found throughout host ranges.

Damage. – Adults puncture holes in current needles (fig. 132) and through needle sheaths. Dried up portions of the needles are blown off by wind or broken off by rain and snow. Chunks of needles may be eaten leaving a saw-toothed edge (fig. 133). Larvae may feed on roots.

Identification. – Magdalis adults are black and may be seen puncturing holes in new needles from late June through August. They are about one-fourth inch long, and have prominent curved beaks. Eggs are laid on twigs in late August. Larvae feed on cambium and wood tissue beneath the bark.

Scythropus, known as the elegant weevil, is broad nosed and scale covered. It is metallic blue-green, gold, brass, or bronze colored and about one-fourth inch long fig. 134). Habits for both weevils are similar, except that Magdalis more often feeds on fresh slash than does Scythropus. Similar damages. – Damage of the two species may be confused, but Scythropus feeds by puncturing needles whereas Magdalis removes chunks of needles. Adults are distinct. Adult

Figure 134 - Scythropus adults are metallic-looking and lack long beaks.

Link to Elegant Weevil 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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