THE 1?EP0RT OF THE No. 36 



in all of these plots raiiiiod i'roiu ])er cent, to 1 per cent., whereas the plants in the 

 chock plots were destroyed to the extent of 52 per cent.. 57 per cent.. 61 per cent., 

 6() per cent., 70 per cent., and 80 per cent, respectively. 



Discs Used. IIe-\a*ional disc (hlock 19) : small square disc (block 21) ; 

 large square disc (block 2i) : and round disc (block 23). All gave excellent pro- 

 tection. In blocks 19 and 24 (100 plants in each) 100 per cent, results were 

 obtained; in block 21 of similar size 1 per cent, destruction occurred and in the 

 fourth block (23) 2 per cent, destruction. In the two check blocks, Nos. 20 and 

 '32 (30 plants in each) the loss from maggot was 10 per cent, and 17 per cent, 

 respectively. 



Tobacco and Lime. One part tobacco dust and 2 of lime, also in propor- 

 tions 1-3 and 1-4. Block 25, 1 to 2; Block 27, 1 to 3; Block 28, 1 to 4, (100 plants 

 in each) had 4 applications about ^ to 1 inch of the mixture being placed around 

 the stem of each plant. Block 30, 1-2; Block 31, 1-3; Block 33, 1-4 (100 plants 

 in each) had three applications. Block 34, 1-2 (100 plants) ; Block 36, 1-3; Block 

 37, 1-4 (150 plants in -each) had two applications. The percentage of plants in 

 these blocks destroyed was also very small, varying from 1 per cent, to 4 per cent., 

 the latter percentage being in Blocks 36 and 37 which received two applications 

 only of the more diluted mixtures. Three applications of the mixture was prac- 

 tically as effective as four applications, and the weakest mixture gave practically 

 as good results as the strongest. Check blocks (20 plants in each) with these 

 series, were destroyed as follows : Block 2(), 25 per cent. ; Block 29, 20 per cent. ; 

 Block 32, 30 per cent. ; Block 35, 30 per cent. ; Block 38. 30 per cent. 



A larger plantation of later cabbages, -3,360 in number, planted May 21st, 

 was used for corrosive sublimate solutions solely. The jjlantation was divided into 

 11 blocks, 8 of equal size, each consisting of 378 plants, and the remaining three, 

 which were used as check blocks, contained respectively, 10-5 plants each and one 

 21 plants. The corrosive sublimate was used in the same strengths as in previous 

 experiment, namely, 1 oz. to 10 gallons water^l :1.280 (Block A, 4 applications; 

 Block B, 3 applications) ; 1 oz. to 8 gallons water=l :1,024 (Block D, 4 applica- 

 tions; Block E, 3 ap])lications) ; 1 T)Z. to 6 gallons water=l :768 (Block G, 4 

 applications; Block H, 3 applications) ; 1 oz. to 4 gallons Avater=l :512 (Block J, 

 4 applications; Block K, 3 ap])lications). Blocks C, F, I and Ij were used as 

 checks. Blocks A, 1), G and J were treated on May 27th, .June 4th, June 13th, 

 and June 24th ; Blocks B, E, H and K, on the first three dates only. In this 

 exj)eriment the time required to treat 3,000 plants was 3^-^ hours, using a watering 

 can with spout closed slightly with wooden plug. In this experiment no attempt 

 was made to keep a definite record of every plant. The blocks were examined at 

 frequent intervals and from a practical standpoint no injury took place in those 

 treated with corrosive sublimate. Conspicuous injury, however, was apparent in 

 the check plots and the plants in these latter were certainly not as thrifty as those 

 treated. 



That the cabbage maggot was abundant in the innnediate area of our work 

 in 1919 was well evidenced by the losses which took place on the farms close by. 

 Hundreds of plants of the early varieties were completely killed. 



The above experiment following those conducted by us previously, particularly 

 in 1917 and 1918, certainly strengthens the belief that in corrosive sublimate 

 we have a valuable control measure for the calibage maagot. 



