June, '22] sasscer and weigel: greenhouse fumigation 203 



insects; as for example, roses can be safely fumigated during the 

 resting period at the rate of 2 ounces of Sodium Cyanid per 1000 cubic 

 feet of space, whereas, in the forcing period ]/i ounce may cause serious 

 injury under unfavorable conditions. In commercial fumigation, 

 therefore, these conditions must be borne in mind, it being understood 

 that a house should not be fumigated until the maximum dosage for 

 the plants involved has been determined. 



The experiments summarized below were conducted after preliminary 

 tests had been made to determine the necessary dosage to kill the 

 insects, and at the same time not injure the plants. 



Conclusion 



The results contained in the above table indicate that: 



1. The common greenhouse insects can be controlled by persis- 

 tently using weak dosages. 



2. These dosages, under the proper conditions, will not reduce 

 the market value of the plants. 



3. Greenhouse plants for the most part show decided stimulation, 

 resulting ultimately in a greater financial return. 



4. Large houses may be satisfactorily separated by the use of canvas 

 or muslin curtains, thus obviating a serious problem of the past in open 

 range houses. 



5. It is evident from the results thus far obtained that some 

 plants m.ay be fumigated while in bloom_ without injury to the flowers; 

 for example, carnations and orchids. 



Aside from, the above facts, the cheapness of fum.igation as contrasted 

 with the cost of sprajnng is an additional argum.ent in favor of this 

 m.ethod of controlling insects in com.mercial greenhouses. 



Formula Employed: 



For each ounce avoirdupois of Sodium Cyanid (containing approximately 51% 

 cyanogen), \yi, liquid ounces of Sulphuric Acid (1.83 specific gravity) and 3 liquid 

 ounces of water were used. This is a slight divergence from the formula which has 

 been generally accepted owing to the necessity of securing sufficient dilute acid to 

 submerge the cyanid. Under greenhouse conditions, it is necessary to use a number 

 of generators in order to secure an equal distribution of ..he gas, and as this number 

 is increased, the amount of chemicals in each generator is proportionately decreased, 

 which will result in poor generation unless there is a slight excess of water. If it 

 were possible to have a number of small generators considerably constricted at the 

 bottom it would be possible to get a satisfactory generation with the l-l>^-2 formula. 



Mr. R. L. Webster: I would like to ask Mr. Sasscer what condi- 

 tions he thinks are favorable to fumigation injury? 



Mr. E. R. Sasscer: There are a nimiber of factors which may cause 

 injury. Fumigating in the daylight, fumigating when you have a 



