352 



Bulletin No. 112. 

 Effects of Experimental Summer Spray. 



IJambarffy 



From this it will be seen that 75 leaves bearing 49,000 scales 

 were examined from the tree sprayed July 3, and that only 33 per 

 cent, of the scales on this tree had been killed. In this case a first 

 inspection was made ten days after the spray was applied, and a 

 second, seven days later. The trees sprayed once July 11 — at the 

 middle of the hatching period — and fr^m which 50 leaves bearing 

 19,000 scales were examined, showed a ratio of benefit of 64 per cent. ; 

 that is, 64 per cent, of the scales alive when the spray was applied, 

 were dead a few hours later. In other words, by postponing the 

 treatment from the 3d to the i ith of the month the effect of it had 

 been nearly doubled. A similar but somewhat greater effect was 

 produced lay single treatments given July 19 and 20, when the 

 greater part of the eggs were already hatched, 68 per cent, of the liv- 

 ing scales among the 281,000 borne by the 150 leaves examined being 

 thus killed. The most effective treatment was a double spraying, 

 one application at the middle and the other about the end of the 

 hatching period, which, as shown by an examination of 57,000 scales 

 from 100 leaves of the tree so treated, killed 82 per cent, of the 

 scales alive when the tree was sprayed. That is, the effect of the 

 operation had been increased approximately 28 per cent, by the sec- 

 ond spraying. 



A comparison of the scales on the two surfaces of the leaves 

 showed that the ratio of those killed on the lower surface was only 

 72 per cent, that of those killed on the upper surface. This was doubt- 



