Willow trees are deciduous trees or shrubs and members of the salix family. Varieties such as the white willow often reach heights of 70 to 100 feet and a diameter of three to four feet. Commonly located near water, willow trees are susceptible to damage from bark-boring insects.
Two types of bark-boring beetles affect willow trees. One is a weevil known as the willow borer, which is native to Europe and Asia and has spread throughout southern Canada and the northern U.S. Adult beetles are dark brown and mottled with light grey colours. Ambrosia beetles infest willow trees that are under stress or freshly cut and enter the tree at ground level, states the University of Florida, IFAS Extension. This small, dark brown beetle was first found in South Carolina and has spread south to the Gulf Coast and north to Maryland.
Willow trees infested with bark-boring insects often have holes scattered about their bark. Other symptoms include sap oozing from bored holes; gnarled, distorted branches; boring dust in holes; and wilted foliage. An infestation of boring insects can also predispose willow trees to attack from fungal diseases.
Since bark-boring insects attack willow trees under stress, keeping trees healthy may prevent infestations. Avoid wounding willows with lawnmowers or pruning tools, which gives insects entrance areas. Nonchemical controls such as black-light and pheromone traps may control light infestations. However, heavy infestations often require chemical treatments, which are most effective if applied during the period in which adult borers lay their eggs, states Colorado State University Extension.