EXPERIMENT STATION WORK WITH INSECTICIDES. 257 



chemicals that mifrht be saved on trees which are not larfje onoiigh to 

 fill the fiiniigator is not worth much consideration. Moreover, the 

 box fuini<;ator does not rest upon the tree and is therefore not likely 

 to cause injury to the buds of the tree or to break oH' the limbs. The 

 dimensions of the box fumi«jator used in the experiments of the sta- 

 tion were (> by G by 10 feet and the light fi-amework was covered by 

 canvas such as is ordinarily used for that purpose. In orchard work 

 in New York the station believes that orchard fumi<j^ation is practi- 

 cable only on comparatively small trees which can be pruned back to 

 12 feet in heijjht and 8 feet in diameter before adjusting the canvas 

 box. For fumigating orchard trees in winter the station recommends 

 the use of 0.8 gram of cyanid of potash for each cubic foot of space. 

 Considerable attention has been given to the study of the effects of 

 hydrocyanic-acid gas upon buds and scions fumigated in gas-tight 

 houses. These experiments have been undertaken partly in response 

 to complaints by certain nurserymen and orchardists that buds had 

 been injured by fumigation. It was evidently necessary that this 

 matter be determined since the present nursery laws of most States 

 recpiire the fumigation of nursery stock, including buds and scions. 

 At the Xew York State Station it was found that fumigation with 

 hydrocyanic-acid gas, using from 0.18 to 0.3 gram of cyanid of 

 potash j)er cubic foot of space in the fumigating house, resulted in 

 no apprecial)le injury to apple, cherry, pear, or plum buds. Peach 

 buds were uninjured when 0.22 gram was used, but showed slight indi- 

 cations of damage when fumigated at the rate of 0.3 gram per cubic 

 foot. During the same experiments it was found that in winter the 

 San Jose scale was not killed when the gas was used at lower 

 strengths than 0.3 gram, while in June the scales were destroyed with 

 a strength of 0.18 gram. 



ARSENICAL INSECTICIDES. 



The experiment stations, as already indicated, have tested a great 

 variety of other insecticides which can not be discussed in this con- 

 nection. Brief mention, however, may be made of some of the work 

 of the stations on arsenicals and one or two special insecticide meth- 

 ods. Paris green is one of the best known arsenical poisons, but its 

 use has b(>en tested at all of the experiment stations and it is com- 

 monly applied by farmers and gardeners for the destruction of leaf- 

 eating insects. Considerable attention has been given by the stations 

 to a study of its chemical composition for the purpose of determining 

 whether the market samples comply with (he laws of various States 

 regarding the maxiinuin (|uantity of free arsenic present and the 

 maxinuun (juantity of total arsenic. 



H. Doc. 924. 59-1 17 



