252 REPORT OF OFFICE OF EXPERIMENT STATIONS. 



trees infested with aphis. The application was made in March. 

 No injury was done to the trees, and the apliis eggs were destroyed 

 by the application. 



In New Jersey" very extensive experiments have been carried out 

 with kerosene and crude oils of all forms. The entomologist in these 

 stations is one of the most enthusiastic advocates of the use of petro- 

 leum oil in some form as a general contact insecticide. In this State 

 crude oil has been used on the peach, pear, apjjle, plum, and cherry 

 without causing any harm to the trees. When, however, the fruit 

 buds of young peach and pear trees were soaked with crude oil a con- 

 siderable percentage of the buds was killed. Undiluted crude oil, 

 undiluted kerosene, and mechanical mixtures of these oils have been 

 used extensively by fruit raisers throughout the State \mder the 

 direction of the entomologist and generally with satisfactory results. 

 As a result of other experiments at the New Jersey stations, it was 

 recommended that crude petroleum be applied undiluted with a 

 Vermorel nozzle, using a small opening so as to obtain an extremely 

 fine mist. It was also recommended that just enough of the oil be used 

 to moisten the surface of the leaves but not enough to produce streams 

 of oil which might collect in various places and burn the bark or buds. 

 The trunk and larger branches may receive a much larger quantity of 

 the oil since the bark of these parts is naturally more resistant. It is 

 recommended that crude petroleum be used with a specific gravity of 

 43° or more and that it be kept at a temperature of about G0° F. It is 

 warmly recommended as a winter application, but considerable pre- 

 caution must always be taken in using it during the summer and for 

 that reason it can not be recommended indiscriminately as a summer 

 spray in the hands of orchardists. Recently the New Jersey stations 

 have carried on investigations to determine the best methods of treat- 

 ing crude oil so as to get a stable mixture with water. These experi- 

 ments, in which certain insecticide manufacturers cooperated, have 

 led to the production of so-called soluble petroleum in a number of 

 forms. This condition was brought about by treating a vegetable or 

 mineral oil with sulphuric acid and adding the mixture to crude 

 petroleum. The effect of this process is to render the crude oil readily 

 miscible with water. In fact it emulsifies almost without mechanical 

 agitation and the emulsion is so stable that the oil does not separate 

 from the water even after being allowed to stand for several weeks, 

 or in some cases even for months. The importance of securing such 

 an emulsion is apparent from the fact that with it a definite per- 

 centage of oil can be obtained and sprayed upon trees w ith the assur- 

 ance that the percentage of oil will remain constant. The New Jersey 

 stations recommend that in that State a soluble petroleum insecticide 



o New Jersey Stas. Buls. 146, 186. 



