45 



Considering the effect upon both the scale insects and the treated 

 trees, the results were slightly in favor of crude oil applied in the 

 form of emtilsion with soap at the strength of 20 or 25 per cent. In 

 many cases 25 per cent oil gave no better results than a 20 per cent 

 strength, the latter proving sufficient to destroy all scales with which 

 it came in contact. Moreover, it was found unnecessary to make more 

 than one application, although the second application doubtless killed 

 some insects that were not reached by the first. No apparent damage 

 to the trees or fruit buds could be definitely attributed to the emul- 

 sion. Trees that received two applications of a 25 per cent strength 

 showed little or no ill effect. 



Equally as good results were obtained from crude oil applied with 

 the mechanical mixing pumps when a uniform discharge could be 

 obtained. The Gould "kero-water" pump with two 20-foot leads of 

 hose was used and, though apparently the best pump of this nature on 

 the market, it can not alwa3'^s be depended upon for a uniform per- 

 centage of oil. For some unexplainable reason the discharge of either 

 oil or water may cease at varying intervals; and even if this regularity 

 lasts only for a moment, a tree may be seriouslj' injured or the scale 

 infesting it may escape unharmed. Moreover, owing to the construc- 

 tion of the pump, a slightly greater percentage of oil is usually dis- 

 charged through one lead of hose than the other; and with nozzles 

 having small apertures (one-twentieth inch Vermorel were used) there 

 is always some separation of the oil and water in the hose and conse- 

 quent variations in the composition of the spray from one instant to 

 another. However, it should be explained that with constant care 

 and frequent tests excellent results can be obtained by the use of these 

 pumps. In the experiments no great difficulty was encountered and, 

 with the exception of a very few injured trees and lack of effect on 

 the scale in rare cases, the results compare favorably with those 

 obtained from the soap emulsion. 



Kerosene. — What has been said of the comparative value of cr^de 

 oil in mechanical mixture and in soap emulsion applies equally well 

 to kerosene, the latter form of application giving slightly more uni- 

 form results in both cases. The results from a portion of the plats 

 treated with kerosene are contained in Table II, which is made from 

 notes on the early applications of emulsion in the Rumph orchard and 

 later applications of the mechanical mixture in the Frederick orchard. 



