102 THE REPORT OF THE No. 36 



trees are often badly weakened by the numerous tunnels in the heartwood and 

 are broken by heavy wind storms. 



Methods of Control. Locust trees are grown in this country chiefly for shade 

 or ornamental trees or in hedges. Any cutting or removal of trees will have to do 

 chiefly with dead and dying trees and branches. It is very important in controlling 

 borer infestations that the infested dying and useless wood be removed and burned 

 before the middle of July, to prevent the spread of the beetles. The dying parts 

 can be identified in the early season, and should be cut out as early as possible, 

 and burned as soon as it has dried sufficiently. 



If the wood is to be utilized the cutting should be done in winter, or before 

 the end of March, the valuable parts barked to destroy the young hibernating 

 larvae, and the worthless remainder completely burned. 



Spraying to Kill the Young Larv.^. The hibernating larvas lie immediately 

 below the corky outer bark and can be killed by spraying the trunks and branches 

 between October and the end of March with a strong contact insecticide. The 

 United States Bureau of Entomology has recommended kerosene emulsion at a 

 strength of 1 part stock solution to 2 parts water for the purpose ; and this strength 

 has been used in our exj)eriments with satisfactory results. 



The Bronze Birch Borer, Agrilus anxius Gory. 



The cultivated birches are being seriously injured by the Bronze Birch Borer 

 throughout much of Southern Ontario, including the Ottawa Valley. The injury 

 is caused by the young of the beetles, slender whitish grubs, which excavate long 

 winding tunnels through the inner hark and sapwood of the small and large 

 branches and trunks. The trees are killed, sometimes rapidly, and in some cases 

 slowly but surely, by successive generations of grubs. A very large number of 

 our finest cultivated birches have already been killed and cut down, and there is 

 good evidence for fearing that it will eventually be useless to plant white birches 

 in the localities infested by the beetle. 



A careful study of the injury was undertaken by the Entomological Branch 

 with the object of finding some effective method of control. We are not yet able to 

 recommend safely any other than the drastic methods suggested by Professor 

 Slingerland years ago. 



The Trees Attacked. The varieties of the European white birch, Beiula 

 alha, are usually planted for ornamental trees in preference to our native species, 

 and have suffered most severely; but our native yellow, white and black birches 

 are killed by the borers when grown under cultivation. We have found the tunnels 

 of the grubs in white and yellow birches in woodlands, but have never known the 

 trees to be killed under natural conditions in the forests. It appears probable that 

 certain varieties or possibly individual trees possess a certain degree of immunity 

 from the borer attacks, and if this proves to be correct we shall have there a partial 

 solution of the problem. 



Evidence of the Injury. The infested tree usually dies gradually from top 

 downwards, but by the time the top is dead the borers will be found working in a 

 large part of the trunk and branches. The inner bark and sapwood may be thorough- 

 ly interlaced with their tunnels without much evidence of their presence appearing 

 upon the outer surface of the bark. The infestation is betrayed to the careful 

 observer, however, in the zigzag or winding ridges upon the branches overlying the 

 tunnels in the sapwood, and in the " rusty " patches upon the trunk and larger 

 branches, where sap is oozing from cracks in the outer bark caused by the tunnels 

 within. 



