The Balsam Wooly Adelgid


Chronic Adelgid damage on Subalpine fir


Bole infestation of Balsam Wooly Adelgids

Bole infestation of Balsam Wooly Adelgids

Here in the Great Northwest, we love our evergreen trees. If you’ve planted Douglas fir, Spruce, Pine, or one of the many other conifer species that thrive here, in your landscape, you’ve likely enjoyed a high degree of plant survival. Most conifers will march along for years without being bothered by an insect or disease issue. If they are, it’s not normally a life threatening situation. Much of evergreen tree mortality will arise from poor planting practices or water and nutrient issues.

There is, however, one enemy of a particularly popular conifer used in landscapes in our area that is responsible for much tree damage and death when left untreated. The Balsam Wooly Adelgid is a tiny aphid-like insect first found in this country in the 1940’s infesting, you guessed it, Balsam firs. It has since spread across the country and is being found on all true fir varieties. It’s preferred host in our area seems to be the diminutive Sub-alpine fir, so often used in landscapes to create that “miniature mountain meadow/rock garden” effect. Slow growing and otherwise a hardy tree, Sub-alpine fir are adapted to high elevation and deep snow pack. Down here in the lowlands, they are a prime breeding ground for the Balsam Fir Adelgid.

Adelgids are an odd insect. There are no males involved in the reproductive process and the eggs laid by the females are genetic clones of the adult. The Adelgids feed on the stems of the tree, enveloping themselves in a white or grayish cotton-like mass, inside which are the purplish-black insects. They can be found feeding on the twigs, branches, or trunk. Heavy adelgid infestations can cover the entire trunk. This is known as a bole infestation and is usually fatal to the tree. The feeding insects cause the tree to form swollen, knob-like areas on the growth nodes and tips of infested branches. Adelgid infestations weaken trees, cause foliage to become sparse, and can kill trees.

Ok, enough of Dr. Doom. If you have true firs and in particular, Sub-alpine fir in your landscape that are suffering from Balsam Wooly Adelgid damage, we can provide a once-a-year treatment solution that will stop the infestation, provided it hasn’t progressed to the trunk of the tree. Preventive treatments on all susceptible fir varieties are highly recommended as Adelgid feeding can be happening well before damage becomes evident. This treatment will also control Fir and Spruce Aphid as well as Cooley Spruce Gall Adelgid. We have treated thousands of firs, with excellent outcomes, over the last twenty years.

We would be happy to inspect your landscape and offer ideas and solutions for happier, healthier plants and trees.

Evan Ogden

Wolbert’s Plant Essentials

Wolbert’s Home Shield