-- These root borers occur throughout the East. Roots of oak and other
hardwood trees are often hollowed or severed. Open-grown trees and those
weakened by disease are most susceptible. Young, vigorous trees are
occasionally cut off at the ground.
Insect (figure 28a). -- Larvae of both species are fleshy, creamy
white with three pairs of small legs. They have cylindrical bodies and
attain lengths of up to 3 inches (75 mm). The adult beetles are robust,
broad, dark brown, somewhat flattened, and up to 1.5 inches (37 mm)
long (figure 28b).
Injury. -- Because injury occurs to the roots below ground, correct
diagnosis is difficult. The above-ground symptoms are gradual decline
of the tree, characteristic of severe, prolonged stress, i.e., leaves
sparse, small, and yellowish. Examination of roots reveal the burrowing
larvae and root damage (figure 28c).
-- Adult beetles emerge from the soil in early summer and deposit 300
to 500 eggs in the soil. Young larvae burrow through the soil to the
roots and begin feeding. The feeding period lasts 3 to 5 years.
-- Disease, drought, mechanical injury, and poor soil conditions increase
tree susceptibility. Therefore, follow cultural practices that will
keep trees thrifty and vigorous. Insecticides are seldom needed.