952. REPORT OF THE DEPARTMENT OF ENTOMOLOGY OF THE 
above (Baumé oil scale at a temperature of 60° F.) is less likely 
to injure the trees than petroleum 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 impos- 
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, 18 pear and 13 cherry trees. 
The plums 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, Il 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 during tests in Table I.—Winter treatment. Trees 
sprayed Dec. 22 to 24. Average temperature of the three days 
39°, cloudy. Weather during the week following usually cloudy 
with average temperature of 29°, 
