Terminal Weevils

Pissodes strobi (Peck), Pissodes terminalis Hopping

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

Hosts. – Engelmann spruce and lodgpeole pine.

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

Damage. – They attack and kill or badly injure terminals on spruce and lodgepole pine reproduction from 1 to 30 feet in height. Leader mortality results in deformity of the main stem or the production of multiple leaders.

Identification. – Overwintering is accomplished as adults or larvae. Adults complete development or become active and lay eggs in the latter part of June. Feeding punctures and egg niches are made in the bark of terminal shoots. Newly hatched larvae initially feed in the terminal just under the bark. Leaders and terminals will begin to droop following girdling, then die and turn gray or brown (figs. 88, 89). Later, they bore into pith where they remain throughout the larval period (fig. 90). Look for oval pupal cells or "chip cocoons' of P. strobi under bark of spruce terminals in August (fig. 91). Adults of both species are typical weevils with long, curved beaks. They are about one fourth of an inch long and have rough wing covers adorned with red-brown and patches of lighter brown or gray scales.

Similar damages. – Damage is similar to that of Eucosma shoot borers or other terminal feeders. Canker diseases can also cause terminal death. Look for distinctive feeding in cambial region of shoots, chip cocoons, or pith mining.

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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