REPORT OF THE STATE ENTOMOLOGIST IQI2 83 
PoP wWSE: OF OLLS ON: DORMANT TREES 
Spraying dormant trees with oils, especially mineral oils, is one 
of the more recent developments of insect control work. The late 
Dr J. B. Smith, late state entomologist of New Jersey, was one of 
the foremost advocates of this practice and at one time took the 
position that petroleum was “harmless to the most tender varie- 
ties and the youngest trees.” It should be added that later this 
pronouncement was modified to “a reasonably safe, economic 
and effective material.” Injury was noted following petroleum 
applications, and shortly the miscible oils were placed on the mar- 
ket and used probably much more generally than was the case with 
petroleum, either pure or in mechanical emulsions. The great ad- 
vantage of the miscible oils is that they make possible a nearly uni- 
form emulsion of known strength and there has been much less 
apparent injury following their use. The ideal in these latter is a 
stable emulsion which can be kept indefinitely, diluted to any de- 
sired strength and which will destroy scale and other insects with- 
out injuring the tree or plant. Some enthusiasts have almost gone 
so far as to assert that injury could not follow the use of even 
large percentages of some of the miscible oils. 
Safety a prime essential. A fruiting orchard represents a 
considerable investment, and we believe that most fruit growers 
rightly consider the safety of the trees of more importance than 
the destruction of an insect pest or the prevention of possible 
injury. The remedy should not be worse than the disease and the 
treatment should most certainly not jeopardize the investment. 
We are unwilling to sanction, even by implication, the use of com- 
. pounds which may result in material injury and, in some cases, 
disaster to the orchard. 
Injury by petroleum. The writer’s experience with petroleum 
and mechanical emulsions of petroleum in 1900 to 1903 inclusive, 
shows that serious injury might result in the latitude of Albany, 
especially if the application was made in the fall or in the spring 
if followed immediately by a spell of humid weather. One fall 
treatment resulted in such penetration and discoloration of the 
inner bark that grave fears were entertained for the safety of the 
trees. A similar condition developed in the spring when the spray- 
ing was followed by several days of foggy weather. 
Others have noted deleterious effects following the application 
of petroleum to various trees in widely separated sections of the 
