(Clemens)
Solomon, J.D. 1995. Guide to Insect Borers in North American Broadleaf Trees and Shrubs. Agriculture Handbook 706. Washington, DC. United States Department of Agriculture, Forest Service. 735 p.
Contents
Hosts
Maple. Silver maple is preferred; red maple and sugar maple are readily attacked, and other maples are probably susceptible. Mountain-ash has been listed as a host (Beutenmuller 1901), but this record needs to be confirmed.
Range
Occurs in Canada, New England, mid-Atlantic region, Midwest, the Mississippi River Valley south through Mississippi (Engelhardt 1946), and west to Nebraska (Holland 1968).
Description
Adult
Black and orange clearwing moth. Wasplike with wingspans of 18 to 22 mm in male and 22 to 27 mm in female (Engelhardt 1946). Wings largely transparent, except for bluish black markings. Head and thorax reddish orange with white and black markings and bluish black antennae. Abdomen and prominent anal tuft vary from mostly black with orange markings to mostly orange with black markings(Beal and others 1952, Engelhardt 1946).
Larva
White with dark brown head and light brown thoracic shield and spiracles. Mature larvae 12 to 19 mm long (Felt 1905).
Pupa
Brown and enclosed in small cocoon of silken threads with excrement pellets and debris interwoven on surface (Holland 1968).
Biology
Moths emerge early in the morning from April to July and swarm about tree trunks, ovipositing on the bark (Holland 1968). Eggs are laid on roughened bark, especially wounds (Felt 1905). Young larvae burrow in bark and cambium and prefer succulent callus tissue at the interface of healing wounds. Tunnels are kept partially filled with frass (Saunders 1881). Each larva maintains its own feeding niches, but several often feed near each other. Larvae overwinter within burrows and make cocoons under bark in spring (Engelhardt 1946). After enclosing themselves in cocoons, the larvae transform to brown pupae. Shortly before moths emerge, the pupae wriggle forward, rupture the thin, papery layers of bark over the tunnel exits, and protrude partly out of the trunk. Soon after, the moths emerge onto the bark. There is one generation each year (Saunders 1881).
Injury and Damage
Round exit holes 3 to 4 mm in diameter in bark typically adjacent to wounds are good evidence of infestation. Brown frass, mostly consisting of small excrement pellets, may be visible at wounds, in bark crevices, or in other rough areas of the bark (Beal and others 1952, MacAloney and Ewan 1964). Borers are found most frequently at the boundary of live callus tissue and dead areas in scars and wounds on the trunks and large branches of ornamentals. Once infested, even minor wounds are kept from healing properly, and heavy infestations can enlarge wounds. Repeated attacks can cause disfigured, gnarled areas on the bark that sometimes ruin the appearance of ornamentals (Felt 1905). Infestations are sometimes recognizable by empty pupal skins sticking out of the bark. Open or loose bark at branch crotches and around pruning wounds may indicate attack. Feeding on the inner bark and sapwood, the larvae, once established, attack year after year, leading to a gradual decline of the tree (Engelhardt 1946). Trees may be girdled or killed by the burrows or weakened so that they are more susceptible to decay and wind damage (Holland 1968). The injuries cause deformities and unsightly scar tissue, sometimes resulting in serious defects in forest stands (Beal and others 1952).
Control
Woodpeckers help to reduce populations in both forests and urban areas (Felt 1905). Artificial control in forests usually is not feasible (Beal and others 1952), but controls commonly are recommended for shade and ornamental plantings. Infested areas on the trunk should be trimmed and cleaned in spring, then painted with tree-wound paint (USDA FS 1985). Insecticides applied to the trunk during emergence and oviposition can prevent reinfestation. In areas of high infestation, planting less susceptible species, such as Norway maple, is recommended (Engelhardt 1946).
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