The Asian longhorn beetle attacks hardwood tree species in the eastern United States, including many that are valued in both urban and forested areas. The beetle completes most of its life cycle inside the host tree, with adults emerging in spring. Adult beetles feed on twigs, leaf petioles and primary leaf veins. Eggs are injected under the bark surface where they hatch into larvae. Larvae tunnel under the bark and destroy the tree’s vascular system which disrupts sap flow of infested trees. Older larvae tunnel into the heartwood where their feeding slowly destroys the structural integrity of trees (Smith and Wu 2008). Trees are slowly killed over a 3-5 year period, although it may be longer.
In their native China about 40% of poplar plantations are known to have been damaged (ca. 2.3 million ha.) by the beetle. 240 cities or counties have been infested in 5 provinces alone (totaling 230 thousand ha), and, an estimated 50 million trees were cut down over a 3 year period in Ningxia Province alone (1991-1993). The beetle causes severe damage from 21-43 degrees north latitude and 100-127 degrees east longitude (represents 4 climatic zones in China: the Transitional Zone between the tropical zone to the south and the warm temperate zone to the north; and the warm temperate zone; the cool temperate zone, and the arid temperate zone).
In the United States, where the beetle was discovered in 1996, an estimated 30-35% of trees in urban eastern states are susceptible to its attack. If the beetle continues to expand its range the potential impacts would be devastating. Urban areas could lose as much as 35 percent of their tree canopy cover and 30 percent of their trees (1.2 billion trees), with an estimated loss of value of $669 billion (GAO 2006). The maple hardwood lumber and sugar maple syrup industries are also put at risk, and tourism associated with the famous fall colours of New England (Smith and Wu 2008). Loss of trees may also decrease property values, cause aesthetic damage and lessen environmental benefits such as cleaning air and water and providing energy-conserving shade. These losses are difficult to quantify (GAO 2006).
If the beetle spreads out of its current urban environment into natural forests, it has the potential to seriously alter the ecological diversity of the natural forests in North America, with additional impacts on wetlands. The potential impact to forests is the loss of 71 billion trees valued at over $2 trillion dollars (GAO 2006).
A further impact of the Asian longhorn beetle in the United States is the cost of eradication measures. “Collectively, from 1997 to 2006, APHIS and the states of New York, Illinois and New Jersey and local governments have spent more than $800 million on ALB eradication measures” (Smith and Wu 2008).