252 Kp:port of the Department of Entomology of the 



above (Baum^ oil scale at a temijerature of GU° F.) is less likely 

 to injure the trees tliau i)eti'oleum of a lower specific gravity, 

 although oils of a lower specific gravity have been successfully 

 used in some instances, notably in Canada. 



REASON FOR EMULSIFYING THE PETROLEUM. 



A very thin film of petroleum covering the entire tree is all 

 that is required to kill the scale. Theoretically, by using a very 

 fine nozzle, the undiluted petroleum might be applied in a thin 

 film but in practice it has been found very difficult if not iui})os- 

 sible to make the treatment thorough without applying a 

 dangerous and wasteful excess. For this reason emulsifying 

 the petroleum with water is desirable as the tree can then be 

 thoroughly wet without applying an excess of oil. 



SERIES I. EXPERIMENTS TO DETERMINE THE EFFECTS 

 OF CRUDE PETROLEUM UPON SOUND TREES. 



ORCHARD i: PLUMS, PEARS AND CHERRIES. 



This orchard consists of 152 plum, 13 pear and 13 cherry trees. 

 The i3lums consist of Monarch, Reine Claude and Quackenboss 

 varieties; the pears Bartlett and the cherries Montmorency. 

 The Reine Claudes, which include about one-third of the plums, 

 are old trees that have been weakened by disease and decay 

 but usually bear a small crop of fruit. The Monarch and 

 Quackenboss trees are sound, especially the latter which are 

 unusually vigorous. The orchard has been kept continually 

 under high cultivation. 



Summaries of treatments and results in Orchard I are given in 

 Tables I, II and III. The checks, which are not given in the 

 tables, consisted of a large number of trees of the same varieties 

 in adjoining rows. In every case they showed no indications 

 of injury during the winter. 



'Weather duviiKj tests in Tabic I. — Winter treatment. Trees 

 sprayed Dec. 22 to 24. Average temperature of the three days 

 39°, cloud}'. Weather during the week following usually cloudy 

 with average temperature of 21)°. 



