New Youk Agricultikal Experiment Station. 265 



by Mr. D. W. Coquillett who made extensive experiments in 

 California. Altliongb it was being extensively used in Cali- 

 fornia it received but little attention in the east until in 1897 

 when Prof. W. G. Johnson took up the problem of successfully 

 combating the San Jos^ scale in Maryland. After extensive 

 experiments he decided that two-tenths gram of 98 per ct. 

 potassium cyanide per cubic foot was sufficient for outdoor fumi- 

 gation of deciduous trees when in the dormant state, that dor- 

 mant nursery trees should be fumigated with .25 gram of 

 cyanide and buds, grafts and scions with not more than .16 

 gram. In connection with these experiments Johnson developed 

 better methods of handling and applying the gas than had been 

 l>reviously in use and called attention to its wide range of use- 

 fulness until now it is employed in green houses, graneries, mills 

 and other buildings subject to infestation by insects. 



In this State the gas is used extensively for fumigating dor- 

 mant nursery trees. Until the past two years, however, but few 

 attempts have been made to use it in the orchard and in this 

 capacity it may still be considered in the experimental stage so 

 far as this State is concerned. 



The experiments reported in this bulletin were begun during 

 the fall of 1900 and continued during the following winter and 

 spring. The principal objects of the experiments were to deter- 

 mine the effects, if any, of the gas upon healthy buds and the 

 strength of the gas required to kill the hibernating scales. 



CONDITIONS. 



The buds were fumigated in small box fumigators made espec- 

 ially for the purpose. For the orchard trees fumigators of the 

 type described in Bulletin 181 were used. All of the fumigators 

 were carefully tested and found to be gas tight. The gas was 

 generated in the manner described in Bulletin 194, page 382. 

 The amount of cyanide used varied from .18 gram per cubic foot 

 of air space to .3 gram as shown in the tables. 



