45 
power of seeds is quickly destroyed, but no injury results to the feed- 
ing or cooking quality of cereals. It can not be employed in the case 
of living plants, nor with moist fruits or products, such as apples or 
bananas. The best results in the case of insects infesting grains and 
seeds, such as Calandra and Bruchus, which are often inclosed in the 
seeds, were obtained by the use of a low percentage (1 to 5 per cent of 
gas) for a period of twelve to twenty-four hours. Employed in this 
way the gas is a very effective means of disinfecting stored grain or 
similar products not intended for planting, and has the additional 
advantage of entirely eliminating the danger of explosion and fire. 
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 ac- 
complished 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 satisfac- 
tory. Preventive work, therefore, should be depended on as much as 
possible, rather than remedial treatment later; the effort being to 
forestall 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. 
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 larve, or any young scales during the growing 
season, are killed in a few minutes, or a few hours at furthest, just 
as any other soft-bodied insect, but the mature scale does not usually 
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