Proteoteras willingana

Proteoteras aesculana

Proteoteras crescentana

Proteoteras arizonae

Proteoteras moffatiana

Synanthedon acerni

Synanthedon acerrubri

Xylotrechus aceris

Ectoedemia populella

Gnorimoschema baccharisella

Aegomorphus morrisi

Proteoteras willingana

Hosts: Boxelder, maple. Boxelder is the major, possibly only, host (Peterson 1958). However, other maples have been mentioned as hosts (MacAloney and Ewan 1964)

Two kinds of injury are important. The first, observed mostly in Canada, is the destruction of dormant buds from mid-August to early fall and from late April to early May (Anonymous 1971). The second, larval burrowing in succulent growing shoots, causes stem breakage stunting, and mortality. Fine, dark brown or black frass often protrudes from entrances a few centimeters below the apex or from the shoot tip. Feeding activity stimulates infested twigs to enlarge abnormally, forming spindle-shaped, gall-like swellings. Larval entrance holes can be found usually toward the lower ends of the galls. Burrows become quite extensive, resulting in tunnels 25 mm or longer. Splitting the swollen shoots reveals tunneling larvae. It attacks trees of any age, from first-year seedlings in nurseries to mature trees in urban and rural plantings. This borer occurs in almost all boxelder plantations in Manitoba, Saskatchewan, and Alberta. Up to 50% of the new growth may become infested with up to 30 twigs infested on a stem. New shoots are often killed or break, and terminal growth is prevented. Heavy outbreaks stunt established trees by killing much of the current tip growth on twigs and branches. Secondary branching results, and when this growth is also destroyed, the affected trees may fork repeatedly, becoming bushy and undesirable as shade trees (MacAloney and Ewan 1964).

Range: Throughout the eastern United States west through the Great Plains. Also found in southern Canada. Most troublesome in the Great Plains of the United States and the Prairie Provinces of Canada, where boxelder is grown extensively for shade and farm shelterbelts (Peterson 1958)

Proteoteras aesculana

Hosts: Maple, boxelder. Silver maple, boxelder, sugar maple, and bigleaf maple have been listed specifically. Other maple species are probably hosts (Craighead 1950, Powell 1962).

Larvae hollow out dormant buds and seeds in fall and continue to feed on dormant buds in spring (MacAloney and Ewan 1964). During the growing season, larvae bore in the current year's shoots, often killing them and preventing terminal growth. Frass, which is ejected from the galleries, is mixed with webbing to form shelters around the entrances. When terminals are killed, opposite lateral shoots begin elongating and often produce forks or other deformities. Larval entrance holes are typically present near the base of current season's growth. When an infesation is sufficiently severe, trees become bushy and disfigured (MacAloney and Ewan 1964). Large trees have been so heavily injured in early summer in West Virginia that they appeared to have been damaged by heavy frost. In the Pacific Northwest, 7 to 50% of bigleaf maple seeds have been destroyed by this borer. Boxelders planted in nurseries and shelterbelts and as ornamentals are often heavily infested in the northern Great Plains, as is sugar maple in the northern Great Lakes area (MacAloney and Ewan 1964).

Range: Transcontinental in distribution across the northern United States and south to Mississippi (Furniss and Carolin 1977, Powell 1962). Discontinuously distributed across Canada, from Nova Scotia to southern Alberta (Prentice 1965).

Proteoteras crescentana Kearfott

Hosts: Boxelder is the major host. Maples have been listed as hosts, but nothing is known of injuries on them.

Larvae bore into new shoots and twigs, which may be stunted or killed, causing loss in terminal growth and deformed or misshapen trees and causing galls to form (Wong and others 1983). The galls are actually abnormal swellings that become elongate to spindle shaped, similar to those caused by P willingana. Dark frass is often present around the entrance holes. Recent studies suggest that previous damage attributed to P willingana was actually due in part to P crescentana (Wong and others 1983).

Range: MD and OH west to SD and south to KS. Common in Alberta, Manitoba, and Saskatchewan.

Proteoteras arizonae

Hosts: California boxelder

Damage: Close inspection reveals small larval entrance holes near the base of current growth. Small amounts of frass may adhere to webbing at entrance holes. Splitting twigs length-wise reveals larval galleries 25 to 35 mm long and virtually free of frass, except near the lower ends of the tunnels. Wilted, dying, and dead twigs may be found scattered throughout the tree crown. This borer does not cause spindle-shaped or gall-like swellings of the infested twigs as does P willingana. 

Range: AZ, NM, CO, CA. Likely in UT and NV

Proteoteras moffatiana

Hosts: Sugar maple appears to be the favored host, but silver maple and red maple are also commonly attacked.

Damage: Larvae bore in the shoots, buds, and petioles. They typically enter terminal buds where leaf petioles are attached and eject black frass. Entrance holes are about 1 mm in diameter. When buds are completely excavated, they mine other buds before shoot elongation is completed. In most trees, terminal bud clusters die then the stem dies back to its lateral buds. Damage to either lateral bud is comparatively rare, but when it occurs, one shoot elongates rather than both. Leaves with tunneled petioles drop prematurely, and injured buds are aborted. Tunneled shoots frequently die back. Injury results in growth loss, stem deformities, and branchiness.

Range: NY south to NJ and west to MN

Synanthedon acerni

Hosts: 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

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).

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).

Synanthedon acerrubri

Hosts: Maple, boxelder. Red and sugar maples are favored hosts; other maples may also serve as hosts.

Damage: Larvae often invade wounds made by cossid, cerambycid, and buprestid borers. Invasion prevents or slows callus formation and sometimes enlarges wounds. Sap-stained, sunken, and swollen areas on the bark of branches and trunks of hosts often indicate infestation. Wounds in bark that are slow to close should be inspected. Prying open bark at infested sites will reveal feeding cavities and often tunneling larvae--sometimes six or more at a site. Although some frass may be ejected, much of it is packed under the bark. Branches are sometimes badly scarred and gnarled with numerous round exit holes in the bark.

Range: Found along Atlantic Coast through the eastern half of the United States and northward into Canada.

Xylotrechus aceris

Hosts: Maple. Red maple is favored. Silver maple, sugar maple, and Norway maple are also attacked. 

Damage: Visible evidence of infestation is swellings or gall-like formations on otherwise smooth stems. Bark begins to break away at the entrance, exposing wood darkened by decay. Fine yellowish frass may be present at gallery entrances. Dissection of infested stems reveals a small cavity under the bark and a gallery 7 to 12 mm in diameter extending 5 to 12 mm horizontally into the stem, then turning 8 to 13 cm straight up. Attack sites sometimes resemble disease cankers. Young saplings 4 to 7 cm in trunk diameter, particularly those in the understory, are most susceptible, but attack sites have been found in trunks up to 10 cm in diameter. Attack sites are most common in trunks but sometimes occur in branches of larger trees. 

Adults leave round exit holes, 4 to 5 mm in diameter usually in the galled, distorted bark near entrance sites. Swollen, irregular scars that remain on the stems for several years are evidence of previous attacks.

Range: Eastern US south to NC and GA and west to MI and in southern Canada

Ectoedema [sic] populella 
Aspen petiole gall moth

Hosts: Poplar. Populus grandidentata, tremuloides

Globular to cylindrical, pea-sized galls form on the petioles just below the leaf-blade. Galls are the same color as the petiole and mostly 4 to 7 mm in diameter, but a few reach 10 mm in diameter. Heavily infested trees may have galls on nearly every leaf petiole. Heavy attacks cause early leaf fall in many shelterbelts or on shade and ornamental trees, but the impact generally is light.

Range: North central and northeastern US and from Manitoba to the Maritime Provinces in Canada

Gnorimoschema baccharisella
Coyote brush gall moth

Hosts: Baccharis pilularis

The larva bores into the apex of the growing terminal for a short distance and seals the entrance completely with frass. A hollow gall forms around the larva, beginning at the farthest point of the larval entry. The twig usually continues to grow, leaving the mature gall some distance from the tip. The gall is short, cylindrical, often spindle-shaped, and may persist for several years. Its outside wall resembles and is confluent with the bark of the stem. Mature galls are 17 to 36 mm long. Later, the larva chews an exit hole in the gall. The larva deposits frass at the apical end of the gall during most of its development. Galls are prevalent and can be found on nearly all plants in heavily infested areas. Infested twigs die and fall off, causing noticeable pruning.

Range: very limited known distribution in the San Francisco and Berkeley areas and southern Monterey County in CA

Aegomorphus morrisi

Hosts: Tupelo. Has been found in water tupelo and blackgum (Craighead 1923, Lugger 1884). Yellow-poplar has been mentioned as a host, but this report seems questionable (Beutenmuller 1896)

Injury and Damage: Small to large areas of loosened bark, sometimes with coarse frass protruding from bark openings provide good evidence of infestation. Removing the bark reveals a large irregular cavity 5 to 8 cm in diameter packed with fibrous frass. Splitting an infested stem reveals the entrance and cavity under the bark, gallery, and exit. Bark scars resulting from previously healed attacks consist of rather large patchy scars with small round scars directly above. Attacks have been found on saplings from about 5 to 12 cm in diameter and at heights from slightly above ground to about 1.8 m. Populations are small and widely scattered; thus, overall damage has been minor. 

Range: Reported only from a few widely scattered areas in eastern North America including South Carolina, Missouri, Pennsylvania, and Canada (Blatchley 1910, Craighead 1923). More recently, it has been observed in the Ozark Mountains of Arkansas, loessal bluffs of Mississippi, and river bottomlands of Florida. 

Guide to Insect Borers in North American Broadleaf Trees and Shrubs