172 PROCEEDINGS OF THIRTY-THIRD FRUIT-GROWERS i CONVENTION. 



injure tree or fruit, has been proven to be erroneous, as double this 

 amount of chemicals has been repeatedly used upon a commercial scale 

 during every month in the year, without injury to tree or fruit (except 

 in a few instances where some of the fruit in its young stage was in- 

 jured), and for experimental purposes as much as two hundred per 

 cent has been added to the strength of the first named formula, with no 

 injury to tree or fruit. Doubling the old formula, however, seems to 

 be perfectly effectual for entire eradication of purple scale and red 

 scale, and some tests made have seemed to indicate that slightly less 

 cyanide was effectual upon the red scale. So far as demonstrated in 

 the work of the Los Angeles.Commission, one and one half to two hours' 

 exposure to the gas is necessary. A slight addition is made to the 

 proportion of water used to dilute the acid and retard too rapid 

 generation of the gas, but it should not exceed three and one half parts 

 of water to one of acid. This, with many other phenomena presented 

 by the practice of this method in the district where it originated, 

 together with the added importance given to the whole subject of insect 

 control by the very exhaustive investigations made by Professor 

 Powell of the Department of Agriculture at Washington, in which he 

 clearly proves that only clean fruit is profitable, moved the then 

 Secretary of the Los Angeles Horticultural Commission to try to 

 bring about a scientific study of the whole process of cyanide fumigation 

 on the part of the Department of Agriculture at "Washington. This 

 movement was taken up by the Los Angeles County Commission, and, 

 with the hearty cooperation of the commissions of other counties and 

 of many large citrus associations, an appropriation of $5,000 was 

 secured from Congress for the purpose, and Prof. C. L. Marlatt, assisted 

 by Professor Woglum, has already inaugurated the work in Los 

 Angeles County, and the whole subject will be fully exploited, covering 

 such points as life of eggs, periods of light and heavy doses, its gen- 

 eration, killing effect, pressure of gas, different proportions of water 

 used, margin between efficiency and danger to tree and plant, external 

 conditions, light, heat, moisture, etc., quality of materials, physiological 

 effects upon tree and fruit, and many other important features not 

 known to commercial fumigators. It must be understood that treatment 

 requiring such excessive amounts of chemicals should not be undertaken 

 when natural conditions are not favorable, such as periods of excessive 

 moisture, or during daytime. Both cyanide and acid must be of good 

 quality, the former not too finely powdered, unless two or more 

 generating pots are used to each tree, and every detail of the process 

 must be carefully handled, but with such care that there need not be 

 the least injury to the tree, even when three times the amount of cyanide 

 used for black scale treatment is used. And needless to say, no scale 

 pest has survived such treatment. 



