38 
GENERAL CONSIDERATIONS ON THE CONTROL OF INSECTS. 
ADVANTAGE OF PROMPT TREATMENT. 
The importance of promptness in the treatment of plants attacked 
by insects can not be too strongly insisted upon. The remedy often 
becomes useless if long deferred, the injury having already been accom- 
plished or gone beyond repair. If, by careful inspection of plants from 
time to time, the injury can be detected at the very outset, treatment 
is comparatively easy and the result much more satisfactory. Pre- 
ventive work, therefore, should be done as much as possible, rather 
than waiting for the remedial treatment later; the effort being to fore- 
stall any serious injury rather than to patch up damage which neglect 
has allowed to become considerable. 
KILLING INSECTS AS A PROFESSION. 
It may often happen that the amount of work in a community is 
sufficient to induce one or more persons to undertake the treatment 
of plants at a given charge per tree or per gallon of the insecticide 
employed. Where this is the case, and the contracting parties are 
evidently experienced and capable, it is frequently more economical in 
the end to employ such experienced persons, especially when a guar- 
antee is given, rather than attempt to do the work one’s self with the 
attending difficulty of preparing insecticides and securing apparatus 
for work on a comparatively small scale. In California this is a com- 
mon practice, and also in some of our Eastern cities, and has worked 
excellently. 
THE DETERMINATION OF THE RESULT OF TREATMENT. 
It is often of importance to know when and how to determine the 
effect of any treatment applied directly to insects exposed on the sur- 
face of plants. In the case of scale insects, especially during the dor- 
mant condition in winter, the response to insecticides is very slow and 
gradual. The scale larvee, or any young scales during the growing 
season, are killed:in a few minutes, or a few hours at the furthest, just 
as any other soft-bodied insect, but the mature scale does not usually 
exhibit the effects of the wash or gas for some time. Little can be 
judged, ordinarily, of the ultimate results before two weeks, and it is 
often necessary to wait one or even two months to get final conclu- 
sions. In the case of liquid washes the slow progressive death of the 
scales is apparently due to the gradual penetration of the insecticide, 
and also to the softening and loosening of the scale itself, enabling 
subsequent weather conditions of moisture and cold to be more fatal. 
With such biting insects as caterpillars and slug worms after treat- 
ment with arsenicals or other poisons death rapidly follows, the time 
being somewhat in proportion to the size of the larve and their natural 
vigor. Soft-bodied larve, such as the slug worms and very young 
ee 
