What is it?
Ash bark beetles cause damage to ash trees in the Edmonton area. The most common and most damaging species here is the Western ash bark beetle (Hylesinus californicus). The adult beetles are oval, grey and brown beetles about 2-3 mm (1/8 inch) long. The larvae living inside the tree are white, C-shaped grubs with a brown head.
What's the problem?
This insect tunnels between the bark and wood of ash trees. This burrowing girdles branches, causing the leaves to turn yellow in late July and early August.
The beetles usually attack dying or weakened branches, however, during periods of drought or other stress, beetle populations may reach outbreak proportions. As the attacks advance, branch dieback may continue to the point where beetles also attack and girdle the trunk, resulting in tree death.
What can I do?
Regular, proper pruning of dead or weakened branches will remove potential beetle breeding sites.Infested branches should be pruned out and destroyed. Branches undergoing attack can be identified by the presence of tiny holes in the bark and accumulations of boring dust. Sap bleeding from these wounds is also visible.
Weakened, older ash trees should be considered for removal, as they may spread infestations to healthy trees.
Adult beetles overwinter in the bark of the lower 15 cm (six inches) of ash tree trunks. A sticky band wrapped around the trunk about 30 cm (12 inches) above the ground may be used to trap beetles emerging in early April.
A new band installed in early September may intercept some of the beetles walking down the trunk to overwintering sites.