March, 1921. 



SCIENTIFIC A Gil I CULTURE 



12: 



methods of scouting to determine its presence in a 

 district. These men upon their return in November, 

 1919, were immediatel.v put into the field in Welland 

 county to scout the district in closest proximity to the 

 nearest Unitetl States infestation and to act as an assur- 

 ance that we did not have the pest in the area most 

 liable to attack. The snow came early and the men got 

 into the field late. Though a preliminary scouting was 

 attempted it was under the most adverse conditions 

 and no borers were found. 



Meanwhile no rejx)rts of its presence reached the 

 Entomological Branch from the corn growers as might 

 have been expected from the i>osters and general in- 

 formation given out, had the insect become estab'lished 

 and had it been causing any damage. Thus the Branch 

 felt that as yet in all probability we had escaped. The 

 following year, 1920, continuing the educational policy, 

 illustrated posters were again distributed in the dis- 

 tricts most likely to be affected and as in the former 

 year were exhibited in the more conspicuous and fre- 



Map of western Ontario showing area scouted for European 

 Corn Borer in 1920. Townships in solid blaclc were found to 

 be infested, those crossed by the diagonal lines only were 

 scouted but no borers were found. 



quented of public place'?. Notwitlh.standing the further 

 distribution of such warning posters and to make 

 doubl}- sure, a scouting party was sent into Welland 

 county in the latter part of the summer and to our 

 consternation the scouts had not been in the country 

 for more than three days when borers from corn were 

 sent to the Branch at Otawa and identified as the 

 European Corn Borer. 



The scouting activities were immediately reorgan- 

 ized in cooperation with Professor L. Caesar, Provin- 

 cial Entomologist, of the Ontario Department of Agri- 

 culture. Two parties were formed, the members of 

 which scouted in the 13 counties most likely to be in- 

 fested. Of the 105 townships in which scouting was 

 done 35 were infested. 



The town.ships in which the coi-n borer was present 

 comprise two separated invasions, areas of different 

 sizes and intensity of infestation, the smaller one made 

 up of the 5 townships of Wainfleet, Hiiinberstone, 

 Bertie, Moulton, and Sherbrook iu the counties of 



Welland and llaldimand, an area of about 340 square 

 miles, in which the infestation is very light and the 

 damage slight ; a larger one consisting of the 29 town- 

 ships of Dereham, Norwich north, Norwich south, Ox- 

 ford north, Oxford west, Missouri ea.st, Dorchester north, 

 Westminster, Deleware, Caradoe, Missouri west, London, 

 Biddulph, Lobo, Adelaide, Metcalfe, Ekfrid, Mwii, Bay- 

 ham, Malahidc, Yarmouth, Dorchester south. South- 

 wold, Dunwich, Aldliorough, U.sborne, Zone, Oxford, 

 Howard and Harwich in the counties of Oxford, Mid- 

 dlesex, Elgin, Huron and K«nt, an area of about 3430 

 square miles. It is in this area in which corn is grown 

 as a commercial crop and which is in immediate proxim- 

 ity to the still other important corn-growing counties, 

 the balance of Kent, Essex and Lambton, tliat we have 

 the most widespread infestation and in which it has 

 attained its greatest intensity and is doing the greatest 

 damage as a corn pest on this continent. 



A study of tlie insect within this area shows that it 

 is markedly at its worst in the essentially flint corn 

 growing region immediately .south of St. Thomas, be- 

 ing distinctly worst in the Union Village area. How- 

 ever, anywhere between St. Thomas and the lake 

 Tremely badly infested fields of flint corn are common. 

 The region of worst attack is approximately an oval 

 area. about 7 miles north and south and about 10-15 

 miles ea.st and west, the western edge being about 2 

 miles west of Union Village. From this centre of 

 severe injury the intensity decreases rapidly westward, 

 eastward and northward till it tapers out entirely in 

 the marginal townships of the infested zone. However 

 even as far north as Strathroy, spots in the flint corn 

 fields are still found w^here a large number of the stalks 

 have fallen down before harvest time. These were not 

 studied and the infestation in these fields cannot be ex- 

 actly stated. 



The most im])()rtant and immediate problem from 

 the point of view of the grower and the one upon which. 

 to base the scope of our control effort was, of course, a 

 determination of the probable damage to be expected 

 from this insect. Hence the investigational activities 

 during the autumn of 1920 took the form of studying 

 as completely as possible to what extent the corn crop 

 was actually being damaged and what the prospects of 

 damage might be for the future. With this object in 

 view the preliminary work was carried on in the centre 

 of the most badly infested part of the large area, though 

 not in the worst fields as it was afterwards discovered. 



The degree of infestation here was much more in- 

 tense in the flint corn than in dent and as a fairlj- com- 

 plete .study was made of the condition of the flint corn 

 crop on the Hathaway Field near St. Thomas, all the 

 figures presented on the chart (See Fig. 2) refer to the 

 study in that particular field. The dent corn was much 

 less severely affected than the flint and will be discuss- 

 ed .separately after dealing with the former. 



The injurious stage of this in.sect is a small greyish 

 white <-aterpillar, when full grown about 1 inc^i long, 

 which may be found boring in almost any part of the 

 corn plant. The adult stage is a small pale yellow 

 (female) or reddi.sh brown (male) moth with a wing 

 expanse of about IVs inches wliich we suppose, from 

 what is known of the life-history in New York, flies in 

 Ontario in late June and July. It lays its eggs chieflv 

 on the under side of the leaves of the corn plant and 

 probably to a slight extent upon the neighboring weeds 

 of which we have found 8 species infested. 



These eggs are laid in small irregular, flat masses of 



