Western Poplar – Agrilus granulatus populi

Western Poplar (Agrilus granulatus populi) Latin Name: Agrilus granulatus populi Common Name: Western Poplar Appearance: Both male and female adults are rough-surfaced, snout-nosed weevils, about 8-10 mm long. They are mostly dull, dark brown to black, and mottled with light brown and gray scales. The hind third of their elytra are usually gray; sides of thorax and parts of legs may be whitish or pinkish. Eggs: Eggs are 1.1 mm by 0.8 mm, white, found in groups of 1-4. Larva: Larvae are creamy-white, C-shaped, legless grubs with reddish-brown heads and a full-grown length of approximately 1 cm. Pupae: Pupae are likely whitish and about 1 cm in length Host plants: Quaking aspen and cottonwood recorded; other Populus species probably also used Territory: Found throughout southern Canada and northern U.S. Damage caused by Western Poplar: Larvae initially expel frass, which is found mixed with oozing sap on bark outside of holes. Later, frass is found in tunnels. Young stems, 2.5-10 cm diameter, are infested primarily around the base, and are killed by larvae mining or by breakage of weakened stems. Adult weevils may also cause injury by feeding on succulent bark of branches or main stem before mating. The most pronounced injuries are old bark scars that are horizontal and deep, and often have right angle extensions and exposed stained wood. Stems that have been repeatedly attacked are often honeycombed with tunnels making them susceptible to decreased wood quality, breakage, and mortality. Stems in moist areas along streams and ponds are frequently attack. Life history and Habits: Adults emerge in summer (May-June in south; July-August in north), feeding on foliage and bark from new shoots on host trees. Mating begins shortly after emergence. Normally, individual eggs are laid in small crescent-shaped holes gnawed in bark by the female. Eggs hatch after two weeks and larvae begin feeding just under the bark where they spend their first winter. Larvae resume feeding in spring, enlarging and extending their tunnels into tree’s sapwood and heartwood. Larvae can take 2-5 years to mature with life cycles shorter in the south and longer in the north. Throughout their developmental period larvae create and maintain gallery openings to the outside (unlike most other wood borers) through which they push coarse boring dust a frass. Pupation occurs in the stem from April to July, depending on location, and lasts 2-3 weeks. Adults emerge through a gallery opening