REPORT OF THE STATE BXTOMOLOGIST 1901 775- 



trees till the autumn of 1900, when trees 12, 13 and 14 were very 

 badly Infested; and, on account of this close proximity to trees 

 in a similar condition on which the scale bred unchecked during 

 the entire season of 1900, it is very probable that they became 

 reinfested during the gromng season, and therefore their con- 

 dition Sep. 25, 1901, should not be taken into account when judg- 

 ing of the merits of whale oil soap; and the same would be true,, 

 but to a less extent, of trees 31-33. Even after throwing these 

 trees out of consideration, the results are not equal to those 

 obtained with mechanical petroleum emulsions, though the pest 



was well controlled. 



Summary of experiments 



A study of the above records will show that the best results 

 have been obtained with either a 20^ or a 25,%' mechanical emul- 

 sion of crude petroleum. Apparently somewhat better results 

 were obtained by the use of the oil purchased from the Standard 

 oil CO., but this may be parti}' accidental. It is a trifle early to 

 be positive regarding this point. It is certain, however, that 

 either the Standard oil or the crude petroleum obtained from the 

 Frank oil co., Titusville Pa., will give very satisfactory results. 

 The whale oil soap and crude petroleum combinations were very 

 effective, but were not so valuable as insecticides as mechanical 

 petroleum emulsions. Kone of. these preparations injured the 

 trees in the slightest degree. 



The experiments with the whale oil soap solutions show that, 

 while this substance is valuable as a check, it can hardly be relied 

 on when applied in early spring to do anywhere near so thorough 

 work as the crude petroleum emulsions. The reason for the 

 greater efficiency of the crude petroleum is probably found in the 

 greater penetrative action of the oil. The few tests with the 

 undiluted crude petroleum confirm the experience of the previ- 

 ous year and lead us to conclude that it is a very unsafe substance 

 to apply to trees. 



