Source of Early Yellow Birch at Algonquin Park
A quick scan of the forest and reference material provided by the Ministry of Natural Resources have helped me identifiy the Birch Skeletonizer (Bucculatrix canadensisella)as the cause of the broad scale early yellowing of Birch Trees this year on the Edge of Algonquin Park.
This insect occurs right across Canada. Its attacks are restricted to the birches and possibly alder. The adults are small brown moths with diagonal white bars on the forewings. The flight period is from late June to late July. Eggs are laid on the leaves,and the larvae at first construct winding mines in them. Later they feed exposed on the undersurface leaving the veins and upper epidermis intact. Leaves so skeletonized turn brown and drop prematurely.
The birch skeletonizer is more spectacular than injurious. Because most feeding occurs in late August and September it is not as detrimental to the trees as it would be earlier in the season since the injury occurs after the leaves have practically finished manufacturing food for the tree. Defoliation does not seriously affect the tree unless repeated for several years. Trees are seldom killed, although there is some reduction in radial growth and some dying in the tips of the crowns.
I’m not so sure about the limited impact of this critter. In the past year, I’ve noticed a half dozen birch that are leafless on the lower part of our property. this fall, we’ll be taking them down for firewood. Hopefully, next spring, we’ll have all the rest of the birch leaf out as expected.
In the meantime, I’m hoping the undamaged leaves continue to give the showy bright yellow hue, we’re so accustomed to enjoying in early October.