REPORT OF THE STATfi ENTOMOLOGIST 1918 5I 



not all the losses can be fairly attributed to wheat midge. It is 

 evident from the above figures that a serious infestation, 30 to 50 

 per cent white heads, must mean a considerable reduction in the 

 crop. For example, a white head if inches long contained i rudi- 

 mentary kernel of rye and 8 maggots, another 3! inches long bore 

 no grain and contained 12 maggots and a third, 3I inches long pro- 

 duced 14 badly shrunken grains of rye and contained 19 maggots. 

 In other words, the white heads are practically a total loss and when 

 their number reaches 40 per cent or more it must mean a large 

 shrinkage in the crop. Furthermore, this is by no means the total 

 reduction since there may be a considerable shrinkage from the 

 possible maximum in the other heads which, for the large ones as 

 shown by the above tabulation, may approximate 4 per cent, in the 

 medium ones this may range from 9.6 to 18 per cent and in the small 

 ones from 10 to 31 per cent. 



The rye crop as a whole was probably not seriously reduced by 

 wheat midge, though there is no doubt but that the yield of individual 

 fields was considerably lower than it should have been and perhaps 

 reduced to a much greater extent than the farmer realized. Unfor- 

 tunately it has been impossible to get accurate information as to 

 yields from these fields and thus demonstrate the relation existing 

 between examinations of small quantities and the returns from 

 relatively large areas. 



Factors affecting infestation. One of the important objects of 

 the survey referred to above, was to ascertain the conditions favor- 

 able to the wheat midge and if possible point out a practical method 

 of reducing the probabilities of injury in subsequent years. 



It was thought by some that early wheat was less injured than later 

 fields though this does not appear to be borne out either by variation 

 in infestation in fields sown early or late or a difference in injury 

 among the varieties grown, at least so far as the period of maturity 

 is concerned. The time of sowing of winter wheat can have com- 

 paratively little influence upon its ripening the following season 

 because the latter is dependent more upon the weather following the 

 starting of growth in the spring than upon the development of the 

 plant before winter weather stops growth. There was practically 

 no difference in the degree of infestation discoverable between early 

 and late sown fields and, as will be shown later, the varietal infesta- 

 tion appears to depend upon other factors than that of earliness 

 or lateness. 



Deep plowing has been advocated as a method of controlling this 

 pest and yet observations showed the insect to be as abundant in 

 4 



