22 N. J. Agricultural Experiment Stations, Bulletin 355 



the house, where of course it is not available for use against 

 insects. Later as it diffuses downward it reaches the plants on 

 the benches and begins to aft'ect the insects on the plants, it is 

 partially absorbed by condensed moisture on the glazing and on 

 the leaves of the plants, and also it diffuses out through the 

 small cracks in the glazing, around the doors, and in the ventila- 

 tors. The interval between the liberation of the gas by the addi- 

 tion of the cyanide to the acid and water, and the time at which 

 complete diffusion has taken place is rather large when compared 

 with the total time of fumigation for aphis in greenhouses, which 

 may be only 15 to 20 minutes- Any method of liberating the 

 HCN in a more diffused manner, so that the gas would reach 

 all parts of the house at approximately the same concentration 

 at the same time, would tend to lessen the danger of burning the 

 plants, shorten the time of fumigation, and give more complete 

 killing results upon the insects. 



The fact that insects were killed in much less time, and at 

 much less concentrations of HCN when they were enclosed in 

 tight flasks where the concentration was approximately equal 

 throughout the flask, and in which they were not subjected to 

 air-currents which would tend to vary the concentration of gas, 

 shows that a comparatively quiet atmosphere in which the con- 

 centration does not vary, is more effective in which to conduct 

 a fumigation. This line opens up the thought that greenhouses 

 which are regularly fumigated might be piped, as for a sprinkler 

 system, so that definite charges of HCN might be led into them 

 from a generator. This method would have the advantage of 

 simplicity, and w^ould give a much more even distribution of gas 

 than is possible with the use of Jars, as is the usual method. 

 However, a more even distribution of gas could be attained by 

 the use of a larger number of jars, scattered through the house, 

 each provided with a deflector of some sort which would prevent 

 the sudden uprush of heated gas, and allow a more gradual 

 diffusion of it through the house. 



Any method which will allow for a more even distribution 

 of gas in the house will result in a saving in the cost of fumi- 

 gation, as less cyanide would be needed to get the same results, 

 because the large amount of gas, concentrated in the comb of the 

 house, and useless there against the insects fumigated, would be 

 eliminated. The efficiency of the fumigation would thereby be 

 increased, the time shortened, and the danger to the plants ma- 

 terially lessened. 



