266 ReEpoRT OF THE DEPARTMENT OF ENTOMOLOGY OF THE 
As stated at first, many of the tests in different sections of 
the country have not only been made under different conditions, 
on different kinds of trees, or if on same kinds of trees, at 
different periods and applied by different methods, also on trees 
of various sizes, age and condition of vigor. Hence, it is not 
an easy matter to draw comparisons. It is fair to conclude, 
though, that only the better grades of kerosene should be used, 
the difference in price not being sufficient to warrant the risk of 
using the cheaper grades. Even the best grade of kerosene is 
liable to injure trees unless applied at proper seasons by means 
of good apparatus in the hands of careful workmen. 
The results, as a whole, indicate that mechanical mixtures 
ranging from 15 to 25 per ct. can be used on apple and pear 
while the trees are in full leaf with but slight injury to the 
trees; while the use of mechanical mixtures ranging from 10 to 
15 per ct. under same conditions is liable to cause some injury 
to stone fruits. Such dilute mechanical mixtures, however, ap- 
pear to be of value as insecticides only against the young insects 
‘before they have become fixed and cover themselves with a 
waxy scale. 
Apparently a good grade of kerosene can be applied to large, 
vigorous pear and apple trees while they are perfectly dormant, 
and cause but slight injury to the trees, but in this locality 
March 1 is liable to be too late. After the sap commences tv 
move there is more danger of injuring the trees. With ston’ 
fruits, especially peach, the reverse apparently holds good. Tha 
is, the use of even weak mechanical mixtures of kerosene on 
dormant peach is sure death to the tree, while during the period 
in early spring when the buds are swelling, but before opening, 
even pure kerosene can be applied with but slight injury. 
No matter what strength nor what grade of kerosene is used, 
it will not kill the scale insects that are protected by rough 
bark and by buds, nor will it kill those it does not strike. 
CRUDE PETROLEUM SERIES. 
These tests were made, for the first series at Huntington, on 
Long Island; for the second series, at Yorktown, Westchester 
County. The charts given show the arrangement of the trees in 
the orchards and the number and the varieties of trees treated 
with each strength of petroleum. 
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