222 transactions of royal scottish arboricultural society. 



Insect Depredations in North American Forests. 



The following is extracted from the Journal of the Board 

 of Agriculture for June 1910 : — 



" A Bulletin recently issued by the United States Department 

 of Agriculture (Bureau of Entomology, No. 58, Part V.) refers 

 to the very extensive damage done to forest trees in North 

 American forests by insects : Dr A. D. Hopkins, the officer 

 in charge of Forest Insect Investigations, estimates that the 

 loss due to insect pests represents i per cent, annually of the 

 total stand of merchantable timber in the United States. This 

 figure, based on the estimated area and stand of the present 

 forests of the United States, and the average stumpage value, 

 is equal to a value of about 13 million pounds sterling 

 annually. 



" Among the pests which have done widespread damage is 

 the large larch sawfly {Ne?/iatus ertcksoni), which is of special 

 interest owing to its recent extension in Great Britain. As 

 was stated in the recent article in this Journal, March 1910,^ 

 p. 982, this insect is believed to have destroyed, since i88o, 

 from 50 to 100 per cent, of the mature larch over vast areas 

 in the north-eastern United States and south-eastern Canada. 



" Until about eleven years ago nothing had been done 

 towards preventing this enormous damage. Since then inves- 

 tigations have been conducted by the Bureau of Entomology 

 of the United States Department of Agriculture, and satisfactory 

 progress has been made in ascertaining the principal insect 

 enemies of the forests of North America, in determining their 

 life-history, and in devising practical methods of control. In 

 the first instance, a number of the most destructive insects 

 were found to be new to science, while as regards the more 

 important known species little information was available as 

 to their habits ; but it is considered that the advice now 

 available would, ' if properly utilised for practical application, 

 evidently prevent from 10 to 30 per cent, of the annual losses 

 at a very small cost.' 



" The work that has been done is, however, only a beginning, 

 and more purely scientific work on the life-history of insects 

 is needed to provide a foundation of facts on which practical 

 recommendations can be based. The need for trained experts 

 is also very strongly urged." 



^ See Transactions, vol. xxiii. p. 186. 



