Maple callus borer
Synanthedon acerni (Clemens)
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. 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).
Damage pupal skins protruding from bark exit holes. James Solomon,
USDA Forest Service. |
Adult(s) female. James Solomon,
USDA Forest Service. |
Damage. James Solomon,
USDA Forest Service |
[ Contents ]
[ Previous ]
[ Next ]
[ Home ]
|
