46 PROTECTION OF PLANTS, 1918-19 



SOME INSECT INJURIES IN WOODLOTS 



Dr. J. M. Swaine, Chief, Division of Forest Insects, Entomological Branch, 

 Department of Agriculture, Ottawa, Ont. 



Very serious and extensive insect injuries to forest trees, particularly to 

 balsam and spruce, have been spreading for several years in the forests of Quebec 

 and the tAvo neighbouring Provinces. The same or similar troubles are develo- 

 ping in farm woodlands in various places, so that it may be worth while to describe 

 these injuries in their relation to farm woodlots. 



The Balsam Injury 



There are extensive areas of forest in Quebec Province upon which the balsams 

 are dead, dying or more or less badly diseased. The primary cause of this trouble 

 was undoubtedly the great outbreak of the Spruce Budworm that spread over 

 the western half of this Province several years ago. The budworm caterpillars 

 fed voraciously upon the balsam foliage and many thousands of trees were killed 

 outright as a direct result of this defoliation; a much larger number were so badly 

 weakened that even after the caterpillars disappeared they were hardly able to 

 struggle back to a normal condition, and each season many thousands of them 

 are dying. The weakened trees are more susceptible to injury by insects and 

 fungi, and they are being attacked by tsvo species of insects, the Balsam Bark- 

 beetle and the Balsam Bark Weevil, and by two injurious types of /ungi, certain 

 heart rots and a sap rot. 



The Eastern Balsam Bark-beetle 



Piiyokteines sparsus Lee. 



The adult of this species is a very small black beetle, 2 mm. in length, cylin- 

 dric in shape, with sparse erect hairs, and a few small teeth on the posterior end 

 of the wing covers. The adults, one male and several females, enter the bark of 

 dying, weakened or healthy balsams in the early summer. Each female cuts a 

 perfectly cylindric egg-tunnel, in diameter slightly greater than her own, and 

 places the eggs singly in niches arranged alternately along its sides. The egg- 

 tunnels radiate from the central nuptial chamber which together with the entrance 

 tunnel forms the residence of the single male. Each female works the boring dust 

 produced in the course of her excavation backwards into the central chamber 

 where it is finally extruded through the entrance hole by the male. The whole 

 set of egg-tunnels lies between the inner bark and the wood, scoring both. The 



