Hylesinus Varius Wwalas (Ash Bark Beetle)

Ash Bark Beetle in Colorado

Ash bark beetle in Colorado is a parasite of green, white, and autumn purple ash, a particularly favored host. Infestation by ash bark beetle can mimic that of Emerald Ash Borer, so it’s a good idea to keep eyes peeled for it and treat as early as possible. However this insect is different from EAB.


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From Bugwood Wiki:
At least two species occur in Colorado, Hylesinus californicus appears to predominate in the western areas and H. aculeatus in the east. Life history of both species is poorly understood under local conditions but the following is based on information from more northern areas and Colorado observations.

Adult bark beetles cut egg galleries under the bark and larvae tunnel perpendicular to the gallery. These injuries can girdle and sometimes kill branches. On rare occasions entire trees are killed by these insects. Injured limbs and heavily shaded branches in the interior of the tree are most commonly attacked. Transplanted trees can be at special risk. Ash bark beetles may infest almost the entire tree, from finger-diameter branches to the main trunk.

The larvae are pale, legless grubs that develop by feeding under the bark, often extensively scoring into the sapwood. Those developing from spring eggs become full-grown in late spring or early summer and pupate within the tunnels. Adults emerge from the branch and feed on green wood, causing little damage.

There is evidence that a partial second generation is produced in some situations. These may not complete development and overwinter as larvae. Bark beetles that have reached the adult stage move to the trunks at the end of the season to cut hibernation chambers within which they winter.

These pests have become increasingly important within the region during recent years. This is likely due to the general increase in ash plantings and, in particular, the increase in ash that has been damaged or is in decline.

Ash bark beetle outbreaks in Colorado often are related to conditions of growing stress. Well-sited, vigorously growing ash should be at much less risk of attack by this insect. Good cultural practices are fundamental to ash bark beetle management.
We use a systemic insecticide, applied via trunk injection, to treat protect and maintain your tree from April through July.

Read more about trunk injection protection and if you need services:
Insect and Disease Control Options

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