Forest Pests: Insects, Diseases & Other Damage Agents

Ash Borer (trunk borer) - Podosesia syringae (Harris)

Solomon, J.D.; Leininger, T.D.; Wilson, A.D.; Anderson, R.L.; Thompson, L.C.; McCracken, F.I. 1993. Ash pests: A guide to major insects, diseases, air pollution injury and chemical injury. Gen. Tech. Rep. SO-96. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station. 45 p.

Importance. - This borer is a destructive pest throughout eastern North America. Trunk infestation rates of 50 percent are common in shelterbelts of the Great Plains. In the South, trees intended for wood products are degraded and reduced in value. Shade and ornamental trees may be scarred, seriously weakened, or killed. Identifying the Insect. - Adults are clearwing moths that mimic paper wasps in appearance and flight. The wingspan of the moth is about 25 mm. The wings and body are brownish black, and the legs are marked with black, orange, and yellow. Larvae are white, except for an amber-colored head and thoracic shield, and are about 25 to 34 mm long at maturity.

Damage; wormhole defect in green ash lumber James Solomon, USDA Forest Service

Identifying the Injury. - The first evidence of attack is sap mixed with fine frass oozing from small holes in the bark. Later the frass is extruded in small clumps. Circular adult exit holes, often with pupal skins protruding, are found above the irregularly shaped entrance holes. Infestation is greatest in the lower trunk. Lumber sawn from infested trees may exhibit numerous dark-stained, pencil-sized holes.

Biology. - Adults begin emerging during February in Florida and during July in the North. Emergence is completed by the end of July. There is a single brood per year. Eggs, deposited singly or in small clusters in bark crevices, hatch in 11 days. Young larvae mine in the phloem and cambium, then excavate galleries 7.5 to 13.0 cm long in the wood.

Control. - Natural enemies, wound prevention, brood tree removal, burlap trunk wraps, and insecticides help to reduce populations. Pheromone traps are used to monitor moth flights in order to time insecticide applications.

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