20 



SfTENTlFIC AGRICULTURE 



September. 1921 



Natural Control Investigations in Canada 



By JOHN D. TOTHILL, 

 Entomological Branch, Ottawa. 



It has been estimated that about ten per 

 cent of our crops are destroyed annually 

 by insect pests, and this represents a huge 

 monetary loss to the Canadian farmer be- 

 cause it has to come out of liis profits. The 

 farmer is working on a narrow margin, as 

 his profits can scarcely average more than 

 twenty per cent of the value of his crop. If 

 it costs, for instance, about seven hundred 

 and twenty dollars to produce nine hun- 

 dred bushels of one dollar wheat, then the 

 farmer's profit is one hundred and eighty 

 dollars, or twenty per cent of the total va- 

 lue of the crop. Without the insect pests 

 he would have grown a thousand bushels 

 instead of nine hundred and at exactly the 

 same cost. Instead of his profit being one 

 liundred and eighty dollars it would be two 

 hundred and eighty. The insects in tliis il- 

 lustration destroy slightly more than thirty 

 per cent of the farmer's profit, although 

 they (mly destroy ten per cent of his crop. 



The Entomological Branch exists for the 

 sole purpose of reducing this huge monet- 

 ary loss by finding out how to control the 

 various pests. 



There are two methods of control in com- 

 mon use ; the artificial and the natural. The 

 artificial includes the use of poison or con- 

 tact sprays, of repellants (such as sticky 

 bands), of cultural methods of control and 

 so on; and the natural method consists es- 

 sentially in preventing and decreasing 

 damage by seeing to it that all the natural 

 enemies of the pest are at work. These two 

 methods supplement one another and nei- 

 ther is complete without tlie other. 



Natural control investigations have been 

 in progress in Canada for a decade, and it 

 is my privilege to explain what lias lieen 

 (lone and with what results. 



The first project was the iiitro(lucti<m 

 into Canada of the native enemies of the 

 Brown-tail Moth. This insect was a native 

 of Europe that had become introduced on 

 nursery stock into the New England States, 

 whence it had spread into Nova Scotia and 

 New Brunswick. Its chief insect parasites 

 had been left behind in Europe and conse- 



quently it became a first-class pest in its 

 new home. Two insect parasites and a pre- 

 daceous beetle were colonized in large num- 

 bers at vantage points in Nova Scotia, New 

 Brunswick and Quebec. Within a few years 

 of liberation these natural enemies of the 

 Brown-tail Moth became established and 

 distributed over the infested areas. The 

 result of this project has been highly gra- 



Calosoma sypochanta. — This useful beetle now 

 destroys man>- injurious insects in Eastern 

 Canada, where it was introduced to lessen the 

 danger from the Brown Tail and Gipsy Moths. 



ti tying, as there has been a notable de- 

 crease of the Brown-tail Moth in both Nova 

 Scotia and New Brunswick during the past 

 two years. There is no longer any need for 

 viewing the Bi-own-tail Moth situation in 

 the Mai'itime Provinces with alarm, and as 

 a result of the reduction of the numerical 

 strength of the insect the cost of artifi- 

 cially controlling the spread of the insect by 



