63 THE EEPORT OF THE No. 36 



field scale. The last series known as " trial plots " includes methods or material 

 not previously tested by us. 



* In addition to these there were a number of small miscellaneous experiments 

 conducted with a view to determining the exact method of action of some of the 

 chief materials used. 



I. Continuation Plots. 



These plots were situated on a piece of ground 275 ft. long by 30 ft. wide. 

 The plants were set out in rows 2 ft. apart and 18 inches apart in the rows, there 

 being 12 rows each containing 240 cabbages of the Early Jersey Wakefield variety. 

 With the exception of tar paper discs and wire screens, 2 applications of each 

 treatment were made, the first on May 21st, the day the adult flies first made their 

 appearance, and again on May 31st. 



The different plots were arranged in triplicate and each section removed as 

 far as possible from the corresponding one, to make more certain of securing a 

 uniform infestation. The table lists the different treatments and gives the results 

 obtained from each. The figures given are representative of costs at Truro during 

 the past season and would doubtless vary materially in different localities and in 

 different seasons. Since, however, they indicate the actual set of conditions en- 

 countered by us in growing the crop and treating it for the maggot," they are here 

 given. The figure showing cost of production of an acre of cabbage was worked 

 *mt and furnished us by Mr. James Dickson of the Horticultural Department of the 

 C'ollege. 



In the following table showing the results of the different treatments the 

 weight of the heads is taken as the main basis for comparison for several reasons, 

 the most important being that, under our conditions of marketing, sales are made 

 by weight. Consequently, it is simplest to make our calculations on that basis. 

 More important is the fact that this is the only really quantitative way to record 

 results. Simply to give the number or percentage destroyed is insufficient, since 

 many cabbages may be dwarfed or retarded, though not actually destroyed or 

 rendered unmarketable. It would be impossible to record the number dwarfed 

 as a result of the work of the maggot or to indicate in any way the degree of 

 dwarfing, since there is no method of determining from the appearance of the 

 plants just where it begins or ends. On the other hand, the total weight from 

 each plot indicates this in a very exact manner. It also brings out the fact that 

 certain treatments increase the weight of heads produced, irrespective of their 

 insecticidal value. The weight, therefore, is the best method of expressing results 

 of the different treatments. The actual price obtained for the cabbage from each 

 plot has been recorded, since this is the point that most interests the commercial 

 grower and is the ultimate test of the practicability of any treatment. The average 

 price per pound is also an important item, for certain treatments retard and others 

 accelerate the developments of the head. Those that hasten the heading up process 

 result in a higher price per pound, as the earliest cabbage brings the highest price. 



It will be seen that the tar paper discs from which the earth was removed 

 after the first two cultivations, gave the only absolutely perfect stand outside of 

 the wire screens. In weight of heads, in price per pound and in total net profit 

 per acre, this plot is greatly inferior to the one receiving corrosive sublimate 1 — 

 1,000, though this plot lost a single plant. Curiously enough double the strength 

 of corrosive sublimate did not increase the efficiency of the material, but rather 

 appeared to reduce it. Either directly or indirectly the use of this material seemed 

 to bring about a great increase in the weight of heads produced. 



