BWA (Balsam Wooly Adelgid) in Christmas Trees
One pest that I have become acquainted with in recent years is BWA (Balsam Woolly Adelgid). It first showed up in the USA in the 1920s, and really took hold in the Carolinas, impacting Fraser fir in particular. BWA is a small, crawling insect that burrows into the bark of true fir (anything abies) both on the trunk and on branches. BWA seems to have a particular fondness for Fraser fir and Subalpine fir (abies lasiocarpa). Numerous generations of BWA can occur within the same year. The good news is that since they are not winged, the spread of BWA within a field tends to be relatively slow.
Once the adelgid burrows into the trunk or stem of a branch, they utilize the sap from the tree, robbing the tree of nutrients. But more significantly, they affect the ability of the tree to move sap through its branches. The first evidence of infestation in the fir tree is that there is swelling where branches fork. It feels and looks like a knuckle.
Over time, if left untreated, you will notice a loss of vitality in the tree as branches begin to die back and turn a paltry gray. Also, infested Fraser fir, which are normally prolific at producing multiple leaders begin to have trouble producing straight leaders and the tree feels stiff when shaken or manipulated.
So, how does one avoid an unsellable product like the one described above and instead has a marketable one?
Here are a few tips on dealing with BWA (and other pests):
- Spray Dormant Spray Oil on your trees in the late winter. Dormant oil is relatively cheap. One can utilize dormant oil and still qualify for organic farm status. Many growers, including this one, finds that the use of dormant oil reduces the amount f insecticides needed at other times during the year. Dormant oil will kill overwintering eggs of BWA, aphids and mites. Some may survive due to being imbedded in the bark.
- If you have trees that are severely infected with BWA, cull them from your field and burn them.
- Don’t grow Fraser or Subalpine fir in the same area for consecutive plantings. After one cycle, move your next crop of Fraser fir to the far end of your field.
- Consider using Altus as a method of killing BWA during the succulent season. Apply Altus when new growth is fairly young and the first hatch is active. Repeat with a second application in 6-8 weeks. Altus is a new product that has been approved for Christmas trees in Canada.
- Consult with your local horticultural store which supplies products like Altus. They should have information and specialists that you will find helpful.
- Insecticidal soap can also be used in the summer or fall. However, avoid treatment during really hot spells.
by: Paul Hesken
BWA (Balsam Wooly Adelgid) Research Paper
Additionally, avail yourself of educational materials like the following one from the BC Ministry of Agriculture: Balsam Woolly Adelgid