Eastern Ash Bark Beetle
Common Name: Eastern Ash Bark Beetle
Scientific Name: Hylesinus aculeatus (Say)
Photographer:Pest and Diseases Image Library
Question
Recently a windstorm blew over some large spruce trees in the Corner Brook area. These trees died from an unknown source and questions were raised as to what was causing the problem and how it could be fixed in order to prevent further damage.
The Problem
The Eastern ash bark beetle Hylesinus aculeatus (Say) is slowly becoming noticed as a growing problem throughout eastern Canada and as far west as Manitoba. These beetles are known for inhabiting, and as a result killing, many large Ash trees (both green and white) in these areas. The problem is not only that the trees become very unsightly after they die but that they become weakened. The eastern ash beetle usually cannot survive in younger trees; younger trees are stronger and produce more sap than do older trees. Younger ash trees therefore are able to resist the insect invasion through a process known as “pitching out”. After an insect bores into a young tree the tree is able to fill the invasion sight with sap or “pitch”. This pitch fills the hole so that other beetles are not attracted to the pheromones released by the first burrowing beetle and therefor no matting takes place and the tree is able to fight off the invasion. Older larger trees are mainly affected because they lack this ability. As a result they usually die from the invasion. Once these larger trees have been damaged by the beetle there could be a risk of thee tree blowing over or simply cracking off and damaging any property or electrical wiring that may be in the vicinity.
Characteristics
This beetle is very small in size, usually ranging from 2.2 to 3.4mm in length. They have a distinct brown and white pattern on the back due to the white-grey scale covering the brown body. It has a rounded back with the rear slightly sloped. Larva are white and characterized by brown mandibles (which are the first pair of mouth parts, jaw like appendages). Larva also lack legs with the thorax (chest) segments larger than the abdominal (stomach) segments. Adults will fly and burrow into trees in the spring and begin laying eggs. The new adults will burrow out of the bark and begin infesting near by trees. There can be anywhere from one to three generations per year.
Photographer:Pest and Diseases Image Library
Damage
The spread of the infestation can be very rapid. Unfortunately most times the signs are only noticeable after the tree is fully infested or already dead. The first sign of infestation may be the discoloration of the tree crowns (the part of the tree above the trunk) to yellow or red. There may also be the appearance of small holes in the bark surface. The eggs are then located branching off form these holes beneath the bark. These holes are the exit holes of the new adults and are very small usually 1-mm round. these beetles are known for inhabiting many forms of ash, but may also be found in other species of trees such as the spruce trees. Other Canadain boreal forests have been hit hard by damages caused by the bark beetles. The federal government has spent up to $40 million in conservation efforts trying to slow the infestations. The damages are only now starting to be recognized as problematic on the west coast of Newfoundland and Labrador because of the age of our trees. It seems as though Smokey the Bear has saved our forests from fires with such success that our trees and forests are older than most and older trees are more vulnerable to infection.
Photographer:
Dave MacDonald
Photographer:
James Solomon
Photographer:
James Solomon
Control
Once a tree has been taken over by the bark beetle there in not much that can be done to save the tree. Insecticide may be helpful if sprayed around the base of the tree in early autumn. This could kill some of the insects but not all, and will not prevent further infestation. Due to the fack that the bark beetle survives best in the older weaker trees the insecticide is the only defence it may have and is never as good as a natural defence. In order to save surrounding trees an infested tree could be cut down and the wood burned in order to isolate and kill the insect. If the tree is dead and large it may also be a good idea to cut it down for safty reasons. In many neighborhoods on the west coast infected trees are becoming a problem not only visually but there have also been reports of property damage caused by infected trees. Due to the proximity of trees within these urban areas infected tree should be dealt with immediately as to conserve the neighbouring trees. If there is an infected tree on your property get in contact with your local forestry center and take the proper steps in removing the tree as soon as you notice an infection. There are also large scale solutions such as isolating an outbreak by cutting down other trees around the infested trees if in a large enough area. As well the introduction of other insects to kill the beetle such as the braconid wasp and the checkered beetle have proven to have a 90% success rate.
