In addition to the eyed click beetle and the whitespotted sawyer beetle, another insect commonly mistaken for the Asian longhorned beetle (“ALB”) is the broadnecked root borer (Prionus laticollis). The broadnecked root borer is a black or reddish brown beetle, up to one and a half inches long, whose appearance differs from ALB in that it is more robust and does not have white spots. The root borer’s antennae are also shorter than that of ALB – less than a body length in the male (top photo) and even shorter in the female (bottom photo). The female also has a visible ovipositor when laying eggs, unlike ALB.
Similar to ALB, the root borer is considered a pest species of deciduous trees; however, unlike ALB, it is a native species and has a much wider distribution, covering much of the eastern U.S. and southern Canada. As its name implies, the root borer causes damage to the root system of the tree, while ALB damages the upper canopy. The root borer attacks some of the same tree species as ALB, including maple and willow, however, unlike the ALB, the root borer is also a pest of shrubs, fruit trees, pecan, hickory, oak and dogwood.
During the life cycle of the root borer the larvae hatch from eggs laid in soil or under leaf litter and then tunnel towards and feed upon tree and shrub roots. Root borers pupate in the soil before emerging as adults, unlike ALB which pupates in the heartwood of trees. Root borers typically attack weakened trees and shrubs, so to avoid this pest, keep your plants healthy. If you suspect one of your trees or shrubs has root borer damage, it is best to consult a certified arborist or other tree care expert.
Photo credits: Michael Bohne, USFS