119 
These experiments, of course, are too limited to be used for general 
deductions, but they show in the first place the great difficulty of kill- 
ing the particular scale experimented upon, and also that peach trees, 
in the dormant winter condition, can stand applications to the trunk 
and lower limbs of excessively strong mixtures, even pure kerosene 
oil, with no great danger. The fact that the pure emulsion was more 
prompt in its effect than the pure oil is explained by the fact of the 
emulsion being thicker and therefore longer in drying up, while the 
oil, which was of good illuminating quality, evaporated very rapidly. 
The use of applications as strong as the last two can hardly be recom- 
mended except in unusual cases of injury, where the "kill-or-cure" 
method is the only feasible one. Winter treatment, however, will be 
of value in a good many cases, notably with plants having very thick 
and copious leaf-growth, rendering it impossible to spray them thor 
oughly during the summer, and with insects the life history of which, 
and the nature of the plant they infest, make summer treatment imprac- 
ticable or unadvisable. Winter treatment of deciduous trees has the 
advantage also that it requires very much less liquid to wet a tree. 
Experience with particular scale insects. — Reference has already been 
made to winter treatment for the new peach scale, Diaspis lanatus. 
Spring or summer treatment of this scale was very satisfactory in its 
results. In the first place, this scale was very uniform at Washington 
in the period of hatching, the first young appearing April 30 and prac- 
tically all emerging during the first week in May. The standard kero- 
sene-soap emulsion was applied on the afternoon of May 7, and an 
examination the following morning showed that all the scales which 
had escaped from beneath the mother scales had been killed. Most of 
those beneath the scales were also destroyed, the general escape of 
the larvae having loosened the old scales so that the insecticide pene- 
trated beneath them. Following the application there was a very long 
period during which no rain fell, giving the insecticide a favorable 
opportunity to affect the plant, but no injury whatever resulted. The 
young scale insects Avere destroyed in twenty-four hours, and after this 
period rain would have been of advantage in freeing the plants from 
further action of the oil. The application was not repeated, and on 
the 22d of May a few living young were found beneath some masses of 
old scales. The habit of the young of this species seems to be to aban- 
don the old scale and seek a new location entirely free from the pro 
tection of the mother scale; but in some few cases this had not been 
done, and young protected under masses of old scales had escaped the 
application. A few old scales were also observed at this date still liv- 
ing, and without any signs of the formation of eggs in their ovaries. I 
am of the opinion that these scales, which ultimately died before mid- 
summer, weie nonfertilized females, and this condition accounts for 
the prolongation of their existence. 
