City of Parksville parks staff are moving forward with a program to remove several ornamental white birch trees throughout the city, necessary because of the bronze birch borer (Agrilus anxius). The bronze birch borer is native to North America and is known to target all species of birch.
A healthy birch is more resistant to the borer but with the droughts Parksville has been experiencing, most trees are struggling to some extent. Sufficient water and fertilization does help to keep the trees healthy preventing an infestation; however, unfortunately, these efforts are largely unsuccessful once a tree is already infested.
For the information of residents, you may suspect your birch tree has the bronze birch borer if your birch shows signs of branch dieback and thinning in the crown of the tree and/or discolouration of foliage and premature leaf drop. The key identifier is the “D-shaped” adult emergence holes on the branches and trunk. The hole is roughly the size of the D in a typed document. In their experience, parks staff have noted the flat side of the D faces upwards.
More information is available at https://tidcf.nrcan.gc.ca/en/insects/factsheet/283
— NEWS staff, submitted