REPORT OF THE STATE ENTOMOLOGIST I9OO 987 



blowing in a direction opposite to that in which it blew while the first 

 spraying was in progress. An examination of their orchards Sep. 1 1 

 showed that hving scales were relatively very few, and that the trees were 

 in excellent condition. The persistence of the oil on the trees for some 

 weeks is unfavorable to the establishment of young scales, and this is 

 undoubtedly a valuable aid in keeping the pests under control. 



It will be seen that even after spraying a tree with undiluted 

 petroleum, a few scales may escape, doubtless because the oil failed to 

 reach them for some cause or other. The effects on the trees indicate 

 most clearly the necessity of the greatest caution in spraying with such 

 oil. In fact, it can not be advised. These trees were sprayed at a time 

 when they should be most resistant, and several of them were in full 

 vigor and had been scarcely affected by the pest, and they should there- 

 fore, theoretically, be in better condition to withstand the effects of the 

 insecticide. One tree came through the ordeal safely, another lost a 

 number of its limbs and the other two died. 



It is true that subsequent experience has led Dr Smith to regard a 

 crude petroleum not testing 43^ or over on the Beaume oil scale as dan- 

 gerous to use undiluted. Dr Smith states that a safe oil for use in this 

 manner must not only meet the specific gravity test but it must be either 

 a green or an amber paraffin oil, not an asphaltum oil. The above ex- 

 periments show that a heavier oil can be used in a mechanical emulsion 

 without apparent injury to dormant trees and the successful control of 

 the scale by Mr Hart indicates that even if the oil be a light one and 

 therefore harmless in its native condition, it is also very effective when 

 diluted. The dilution saves oil, aids in giving a more uniform distribution 

 of the insecticide and as a coarser spray can be used, the work may be 

 done more rapidly. The outfit necessary for making a mechanical mix- 

 ture is more expensive than an ordinary spraying apparatus but the sav - 

 ing in oil would soon make the difference, if the operations were of any 

 magnitude. An improvement has been made in mechanical sprayers in 

 that the oil and water are conducted in separate tubes to the nozzle, thus 

 preventing the separation of the oil and water in the hose. This device 

 is made by a Canadian firm. A mechanical dilution of crude petroleum 

 is much safer, apparently just as effective and its use is therefore advised. 

 Whale oil soap . The trees were not injured by the application of this 

 insecticide, even at the rate of 2 pounds to the gallon. They were very 

 thoroughly sprayed, and the scale was undoubtedly severely checked, but 

 the results were not equal to those obtained with a 20 % crude petroleum 

 emulsion. The two treatments with whale oil soap solutions left the trees 



