Poplar carpenterworm
Acossus centerensis (Lintner)
From: Solomon, J.D. 1995. Guide to insect borers of North
American broadleaf trees and shrubs. Argic. Handbk. 706. Washington, DC:
U.S. Department of Agriculture, Forest Service. 735 p.
Hosts.Poplar. Quaking aspen is preferred (Bailey
1883). Balsam poplar also has been casually mentioned as a host (Packard
1890).
Range. A northern species occurring from New Jersey west to
Illionois and North Dakota and in Canada from Quebec and Ontario west to British
Columbia (Barnes and McDunnough 1911, Doane and others 1936, Doolittle and other
1976, Felt 1906, Forbes 1923).
Description
Adult. Moderately large, black and gray-mottled moth (Bailey
1883, Felt 1906, Forbes 1923). Forewings covered with black reticulations
over black-gray scaling, shading darker toward base. Hindwings rounded and
translucent with faint reticulation (more conspicuous beneath) in both sexes and
blackish hairs at base. Wingspan of males 40 to 50 mm; females 50 to 64
mm. Head, thorax, and abdomen blackish and edged and shaded with
gray. Sexes more alike than other cossid moths. Females
distinguished from males by their threadlike antennae (feathery antennae in
male) and slightly more robust bodies.
Larva. Creamy white with dark brown head and strong black
mandibles (Bailey 1883, Felt 1906). Thoracic shield pale yellowish to
blackish brown. Thoracic legs well developed with black claws.
Spiracles dark brown and anal shield yellowish. Mature larvae range from
32 to 45 mm long.
Pupa. Narrow, shiny, wrinkled, brownish black, and about 30 mm
long.
Biology.Adults emerge during the day in June and July (Bailey
1883, Doolittle and others 1976); prefer to rest on roughened areas of the bark,
bark scars, or broken limbs. Moths are sluggish and easy to capture but
resemble the bark so closely that finding them requires close scrutiny.
Males are attracted readily to traps baited with synthetic sex pheromone (Dix
and Doolittle 1985). Females deposit eggs singly or in small groups on the
bark, in tunnels, and in other bark openings. Females have been observed
to deposit 50 to 60 eggs in captivity, but probably deposit more in
nature. Larvae bore in the bark and heartwood, often feeding in groups; 17
larvae have been found in a 90-cm-long branch. Larvae of three sizes have
been found, indicating a 3-year life cycle. Mature larvae pupate in the
innermost part of the galleries with their heads toward the openings.
After slightly less than 1 month, pupae work their way to the gallery entrances
and through the frass plugs, and the moths emerge.
Injury and Damage. Attacks occur mostly on trunks and branches
smaller than 31 cm in diameter and occasionally in trunks up to 41 cm diameter
(Bailey 1883, Felt 1906). Heavily infested trunks may have many open
entrances and numerous distorted bark scars from healing wounds.
Dissection reveals many large galleries up to 15 mm in diameter running in
diverse directions deep in the wood. The galleries end in smooth pupal
cells about 40 mm long and often about the same distance from the bark.
Exit openings are typically kept partly closed with wads of debris and frass.
Fine chips and thin slivers are loosely pressed together against the wads.
Empty brown pupal cases often can be seen protruding from bark
perforations. Trees containing wounds, previous marks of borer attack, and
pockets of decay are most apt to be infested. Infested trees sometimes
break at weakened places. Heavily infested trees often succumb to this
borer.
Control. Natural control agents include an unidentified
ichneumonid parasite, woodpeckers, and ants (Bailey 1883, Packard 1890).
Up to 15 ichneumonids have been recovered from 1 host pupa. Ants and birds
destroy many eggs, whereas woodpeckers destroy large numbers of the
larvae. Infestation can be prevented or controlled in high-value trees
with chemical trunk sprays or gallery treatments.
Adult(s). James Solomon,
USDA Forest Service. |
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