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October, '21] penny: oil spays for leaf roller 431 



ly small and consequently the eggs are vety difficult to obtain in large 

 numbers. The eggs are placed almost entirely on the extremities of the 

 branches, on twigs usually not greater in diam.eter than an ordinary 

 pencil. The writer has never observed an egg mass on the m.ain trunks 

 of trees in the Watsonville district and it is indeed rarely that the eggs 

 can be found even on large branches. It is quite evident also that this 

 position factor of the eggs has a direct bearing on the 'degree of 

 killing efficiency that can be obtained, even with a well adapted m.aterial, 

 because of the misses that unavoidably occur in spraying. Within the 

 bounds of economy it is alm.ost an im.possibility to thoroughly wet the 

 extremities, particularly if the trees be large. It might be added further 

 that the comparatively small number of eggs deposited means a small 

 nimiber of worms, each of which is able to do its maximum amount of 

 injury and an}^ spray that tends to reduce the number of worms at all 

 will correspondingly reduce the total amount of injury. 



The best control obtained with any oils in the tests was procured with 

 the emulsion of the Pennsylvania Gas Oil, 10 per cent of which gave an 

 80.9 per cent kill in the sprayed plot. 



The results obtained by dipping eggs in three strengths of this same 

 oil would seem, to indicate that for spraying a 5 per cent dilution is a 

 little too weak while a 15 per cent strength would possibly give a better 

 kill on the trees than 10 per cent. It is the writer's opinion in this case, 

 however, that a 10 per cent emulsion is sufficiently strong and that ineffi- 

 ciency in spraying accounts for the 19.1 per cent of eggs that were not 

 killed. 



The Pennsylvania crude oil in both types of emulsions gave very good 

 killing results with the dipped masses in the 10 per cent and 15 percent 

 strengths. The same can be said of the Calol Diesiel Oil. The failure 

 of the 10 per cent strength of these oils to kill the eggs on the trees is not 

 easily explained, especially since the sam.e strength in dipping was quite 

 effective with all of them.. 



The emulsions of California distillate gave practically no control with 

 any strength, the figures being about the same as the check for both 

 dipped and sprayed egg m.asses. 



The results obtained with Spra-m.ulsion on the trees were aIm.ost 

 negligible and only fair results were obtained with the dipped masses. 

 The count of the eggs from, the orchard sprayed with the Balfour Guth- 

 rie & Company's Miscible Oil No. 1 showed a very low percentage of kill, 

 but as stated before, the writer is in no way responsible for the preparation 

 or application of the spray in this orchard. 



