39 



to prevent the insect from ever causing them any additional injury. 

 The two nurseries that originally distributed the scales are practically 

 clean, and their arrangements for growing stock at the present time are 

 such that I believe that material received from them is about as safe as 

 that received from any district where scale has ever been known to 

 exist. There is no doubt that in the Delaware Valley region the scale 

 has run away. I have every reason to believe, however, that where 

 it has run into wild land it is meeting sufficient natural checks to pre- 

 vent its doing any particular harm to the vegetation that it infests. I 

 am not sure that this escape will not prove to be a benefit for the reason 

 that natural enemies can breed here undisturbed, and if there is such 

 a thing as mastering it these enemies will in due time find their way 

 into our infested orchards. I do not believe it possible to say definitely 

 that any district in which a scaly tree has once stood for an entire 

 season is completely free from the scale. It is known to all who have 

 had any practical experience that it is just as easy for a bird to carry 

 larvre a mile as it is to carry it from one tree to another. Probably 

 most of you have also had the experience of finding isolated or even 

 half a dozen scales on several adjacent trees from which no young had 

 ever hatched. This was due, of course, to the fact that only one sex 

 had been transferred or that the two sexes were so widely separated on 

 the tree that tbe male could not find the female. 



I have been carrying on an elaborate series of experiments during 

 the present summer in the direction of controlling or destroying the 

 scales, and these are resulting very satisfactorily. The season, how- 

 ever, .-S not sufficiently far advanced to give results that may be consid- 

 ered in any way final. 



Mr. Johnson followed with a paper entitled: 



HYDROCYANIC ACID GAS AS A REMEDY FOR THE SAN JOSE SCALE 

 AND OTHER INSECTS. 



By Willis G. Johnson, College Park, Md. 



After a preliminary inspection of the orchards and nurseries upon 

 my arrival in Maryland, I found such an alarming condition of affairs 

 that I deemed it advisable to begin my experimental operations with 

 hydrocyanic acid gas without delay, as I had plenty of material upon 

 which to work. Accordingly, in ^November, 1896, after constructing a 

 fumigatorium, I began my experiments upon badly infested peach, 

 plum, pear, apple, and nectarine stock direct from the nursery, and 

 one-year old pear, plum, and apple trees from the orchard. Many pre- 

 liminary tests were necessary, using the potassium cyanide from 0.12 

 to 0.25 grams per cubic foot of air space inclosed. The time of exposure 

 was also varied from fifteen to sixty minutes. 



