THE REPORT OF THE No. 33 



THE SPREAD AND DEGREE OF INFESTATION OF THE EUROPEAN 

 CORN BORER IN ONTARIO IN 1923 



W. N. Keenan, Division of Foreign Pests Suppression, Department of 



Agriculture, Ottawa 



The first year, 1920, that the corn borer was discovered in Ontario, thirty- 

 five townships were found infested, covering an area of 2,780 square miles. In 

 1921, seventy-one additional townships were added to the quarantine; in 1922, 

 forty-five more were infested and eleven were included in the quarantined terri- 

 tory on account of their situation. The area under quarantine in Ontario at 

 the beginning of this season, 1923, totalled 12,616 square miles, as compared 

 with 13,857 square miles similarly affected in the various infested portions of 

 the United States. 



This season, 1923, scouting of the border territory was again carried on 

 during the months of August and September. All the corn-growing townships 

 between Lake Huron, Georgian Bay and Lake Simcoe were examined as well as 

 the remaining unquarantined townships of the counties of York, Ontario, 

 Durham, Victoria, Northumberland, Peterborough, and Prince Edward. On 

 account of the possibility of water distribution, all the shore townships along 

 the St. Lawrence river, as far down as Cornwall, were inspected and portions of 

 the county of Carleton were also scouted. 



As a result of the above inspection, only eight additional townships were 

 found infested; one in Huron county, three in Bruce, two in Wellington, one in 

 York, and one in Durham county. All of the above townships adjoin the quar- 

 antined territory with the exception of Saugeen and Kincardine in Bruce county. 

 The Saugeen township infestation represents the most northern point of infesta- 

 tion in Canada and in this connection it is interesting to note that several hills 

 of corn were found infested in the field, whereas at the other points discovered 

 this year, only isolated stalks were found infested. The northern spread along 

 Lake Huron again demonstrates the relative importance of lake shore conditions 

 in corn-borer distribution and an effort will be made to watch the development 

 of the pest in the township of Saugeen. 



Possibilities of Further Spread 



From the viewpoint of food supply, it is, of course, possible that the European 

 corn borer may spread over a much larger area in the province of Ontario than 

 it covers at the present time. The reports of the foremen of the scouting parties, 

 who worked Grey county in the past two seasons, would indicate that the interior 

 of this county does not grow corn to any extent. Dufferin county is also unim- 

 portant as well as northern and western Simcoe county in general. Northern 

 Ontario county, Victoria county, and northern Peterborough county may be 

 similarly classified, but corn is a sufficiently important crop in various other 

 uninfested sections of the province to warrant efforts being made to retard the 

 spread. An important portion of Wellington county is still uninfested. A 

 large amount of corn is grown in the shore townships o£ Lake Simcoe, the town- 

 ships bordering the quarantined territory in the counties of York, Ontario, 

 Durham, Northumberland, southern Peterboro, and Prince Edward county 

 usually grow a large acreage of corn, and the townships along the St. Lawrence 

 river would supply a sufficient amount of corn to favour the development of an 

 outbreak. The counties of Glengarry, Prescott and Russell are somewhat 

 important. The county of Lanark grows about 11,000 acres and the county 

 of Carleton ranks fifth in importance in the province in silage-corn production, 

 with about 18,000 acres. 



