April, '15] 



HERRICK: FRUiT-TREE LEAF-ROLLER 



183 



trees we spra^^ed in the Xew York orchard. If it had not been for the 

 fact that we feared the effect of the miscible oil sprays we should have 

 insisted on a more thorough drenching. 



Again, in 1914, a still more extensive series of experiments based on 

 knowledge gained in the previous seasons was planned and carried out 

 in cooperation with two growers at Hilton, N. Y. J\Ir. R. W. Leiby 

 was placed in charge of these field experiments and to his thorough 

 and careful work we are greatly indebted for our results. 



Briefly, three brands of miscible oils were used in a preliminary way 

 on small areas in which the results could be accuratel}^ checked by 

 careful counts of eggs, hatched and unhatched. In cage experiments 

 carried out indoors Target brand killed 94.7 per cent of the eggs while 

 Scalecide killed 96.2 per cent. In the check, 95.75 per cent of the 

 eggs hatched. 



In outdoor experiments confined to a few plum trees on which the 

 egg masses w^ere located and marked b}^ tying strips of w^hite cloth 

 about the branches. Target brand at 1 to 20 killed 92.6 per cent of the 

 eggs, Scalecide, at 1 to 15 killed 91.2 per cent and Orchard brand 87.4 

 per cent. The average for the three oils was 90.4 per cent. Very 

 likely these egg masses being so conspicuousky marked were more 

 thoroughly treated than would be the case in ordinarj^ orchard spray- 

 ing. The results in the main orchard would indicate this. 



In the main orchard, sprayed by the owner in the ordinary waj^, yet 

 thoroughly, an extended count of egg masses showed that an average 

 of 85+ per cent of the eggs were destroyed. In general orchard 

 spraying it is an exceedingly difficult matter to hit all of the egg masses 

 or to thoroughly wet all that are touched with the mixture. It is 

 doubtful if the average grower will be able to kill over 85 per cent of 

 the eggs on large apple trees for the simple reason that some of the 

 masses will not be actually hit with the liquid. If, on the average, 

 85 per cent of the eggs can be destroyed with the miscible oils the}' will 

 constitute a most efficient check against serious infestations of the 

 leaf-roller. 



We did not, however, rely on the miscible oils for the complete 

 control of this insect in the orchards under consideration. We planned 

 to supplement the oils with arsenate of lead and on May 7, the next 

 day after the eggs began to hatch, the orchards were sprayed with the 

 poison at the rate of 3 pounds to 50 gallons of water. The buds had 

 just begun to burst and two or three leaves had separated. 



A second application of lead in the same proportions was made on 

 May 14 just before the blossom buds had separated. Finalh^ on May 

 26 the first codling moth spray was applied. The results were very 

 satisfactory and the owners feel that they can control the leaf-roller. 



