. Canadian forestry journal. Forests and forestry -- Canada Periodicals. 1928 Canadian Forestry Journal, November, 1918 A New Forest Insect Enemy of the White Birch By J. AI. SwAiNi: Chief, Division of Forest Insects, Entomological Brancli, Lttawa A new and highly destructive enemy of the white birch was dis- covered by us this summer in Quebec Province, and serious injury from probably the same cause has just been reported from another locahty. In the region examined by us the disease was evidenced by many dead white birches, visible in every direc- tion, indicating that the outbreak had been
. Canadian forestry journal. Forests and forestry -- Canada Periodicals. 1928 Canadian Forestry Journal, November, 1918 A New Forest Insect Enemy of the White Birch By J. AI. SwAiNi: Chief, Division of Forest Insects, Entomological Brancli, Lttawa A new and highly destructive enemy of the white birch was dis- covered by us this summer in Quebec Province, and serious injury from probably the same cause has just been reported from another locahty. In the region examined by us the disease was evidenced by many dead white birches, visible in every direc- tion, indicating that the outbreak had been in progress for at least several years. Of the living trees probably over 50% are already badly diseased, and show the characteristic d>dng branches in the upper part of the crown. Nature of the Injury. The injury is caused by a small bronze-black beetle, known as the Bronze Birch Borer, Agrilus anxius. The eggs are laid in the bark during June and July. The larvae or grubs excavate long winding tunnels through the inner bark and sap wood of both branches and trunk, and since the mines are frequently very numerous, the sap-flow is checked and the affected portion of the tree may succumb very rapidly. The winter is passed in the larval stage in cells situated in the outer part of the sap- wood, and the adult beetles, having developed from the larvae during the following spring, bore half-round holes through the bark and leave the tree chiefly during June and July. Injured living trees show dying upper branches; when these dead or dying limbs are peeled, the charac- teristic winding tunnels of the larvae on the surface of the sapwood often form a tangled network. Flxtent of the Injury. We do not yet know how widely the injury is distributed through out the Province, but it is ])robably of more than local importance. It ap- pears to be spreading rapidly in the section examined: about 50% of the white birches arc ])adly injured and the remaining healthy trees will apparently be
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