Bark beetles prey on may species of trees. Several of these beetles that have been in the news lately, are active in the Roaring Fork Valley and can kill an untreated tree.
It is not the adult beetle, rather the larvae that does the damage. The female beetle lays her eggs in the bark of a tree, the eggs hatch into larvae and they mine into the growth layers (cambium) of the tree. There they tunnel/feed on the energy rich cambium for a year sometimes two years, pupate into an adult and mine out of the tree as an adult to repeat the life cycle. It is the tunneling/feeding on the cambium that causes the damage, disrupting the flow of water and nutrients up and down the tree.
The biggest threats to our conifer trees are the Douglas-fir Beetle, Mountain Pine Beetle and the Spruce Beetle as these can kill a tree. The Ips Beetle, which can infest both pines and spruce, won’t kill the tree outright but causes significant damage. On the horizon is the Emerald Ash Borer which kills green and white ash. The pest is active on the Front Range and it is only a matter of time before it arrives in the Valley.
Maintaining tree health and with some of these pests, hormone repellents is the first defense. Also, don’t transport firewood, it may be infested. Pesticide applications by trunk injection or trunk application that will kill the feeding larvae is a treatment. These treatments are applied in the spring prior to adult egg laying and the feeding activity of larvae that may be in a tree increases.