Biocontrol of the Emerald Ash Borer pest improves outlook for ash trees in North America
Emerald ash borer (EAB), a pest of ash trees native to Asia, was introduced to North America in wood packing materials used in international trade during the 1990s. This beetle was discovered in Michigan in 2002 and to date infestations exist in 31 states. EAB is now considered the most destructive non-native insect to invade North American forests. In 2007, after three insect species that attack EAB in Asia were approved for release in the U.S., the U.S. Department of Agriculture started the EAB biocontrol program. At study sites in Michigan where these EAB biocontrol agents from Asia were first released, researchers continue to monitor the prevalence of introduced and native natural enemies, and their effects on EAB populations, ash tree health, and forest recovery. During the last 10 years, the sustained establishment and spread of two EAB biocontrol agents released in Michigan has been confirmed. Recent tree inventories at the study sites revealed large numbers of ash saplings and young trees, and the health of this surviving ash correlated with a biocontrol agent that attacks EAB feeding in small-diameter ash trees. These research findings indicate that EAB biocontrol may improve the outlook for ash trees in North American forests in the aftermath of EAB.