August, '09] JOURNAL OF ECONOMIC ENTOMOLOGY 281 



nature is very much the same the world over, and it requires some 

 determination for the nurseryman in the height of the shipping sea- 

 son to demand that his workmen leave the fumigation house closed 

 from 40 minutes to 1 hour, when he needs the stock to fill a number 

 of orders, or to go through the fumigation process twice when he is 

 quite sure the full amount of stock he has on hand can be crammed 

 into the house at one time. 



It is not surprising then that instances have come to our attention 

 where stock that had been fumigated and set in orchards, remote from 

 known cases of infestation with San Jose scale, develop this trouble. 

 The fact that a large amount of adulterated potassium cyanide was 

 on the market at that time also added to the difficulties. 



Reports also began to reach us during 1903 and 1904 in regard to 

 injury from fumigation. "While we were sure, in the light of our ex- 

 perience in fumigation work, that some other agency was responsible 

 for the trouble, careful tests were made during the fall of 1904, from 

 which the conclusion was reached that nursery stock should not be 

 injured b,y fumigation, as ordinarily recommended. In fact, no per- 

 manent injury to dormant trees treated with from 3 to 4 times the 

 normal strength of gas was observed. Injury was noted in case of 

 stone fruits, especially cherry, fumigated with the regular charge late 

 in the spring after growth had started up. Messrs. Symons of Mary- 

 land and Burgess of Ohio carried out similar exi^eriments about the 

 same time with similar results. 



The writer also had a large number of samples of cyanide on the 

 market in the state during 1904 and 1905 analyzed, and found much 

 of it to be impure. The close packing of nursery stock in the fumi- 

 gation house, however, appeared to be one of the main sources of 

 trouble. The writer's experiments on this phase of the question indi- 

 cated that one could not expect fumigation to be effective against the 

 San Jose scale on plants in the far corner of the fumigation house 

 with an exposure of 40 minutes to this gas, even with ordinary 2 

 year apple stock if it is packed tightly. It also seemed impractical 

 either to increase the charge or length of exposure to the gas suffi- 

 ciently to fully compensate for the error of packing stock too tightly 

 in the house. 



Mr. Symons^ found in his recent experiments: "That .30 grams 

 with 30 minutes' exposure is hardly sufficient for fumigating trees 

 known to be infested with San Jose scale (a little greater than ordi- 

 narily recommended) and that with this strength a 45 minute ex- 



'See bulletin 131, Md. Agr. Exp. Sta., College Park, Md. 



