134 FUMIGATION METHODS 



One hundred and fifty to two hundred plants with 

 fronds in all stages of "development have been thus 

 treated two or three times each year for the past four 

 years with no injury to the plants and almost complete 

 destruction of the insect. They were treated fifty at 

 a time in a fumigating box. 



Adiantum cuneatum and A. ballii have been tried 

 on a small scale and were not injured by the treatment. 



Coleus. Golden Bedder, Verschaffeltii, Shy lock, 

 and others; 24,000 plants in pots, badly infested with 

 the white-tailed mealy bug, Orthezia insignis. The 

 house contained 15,587 cubic feet of space. Treated 

 at the rate of one-tenth of a gramme of 98 per cent, 

 cyanide of potash per cubic foot of space for twenty 

 minutes, one hour after dark. Orthezia all killed and 

 plants not injured in the least. All other means of 

 destroying the Orthezia had been tried without effect. 

 Large numbers of the common mealy bug were also 

 killed by this treatment; but it was not nearly so 

 effective as for the white-tailed mealy bug. All coleus 

 cuttings made by the United States Propagating Gar- 

 dens for the past few years have been fumigated before 

 being prepared for the cutting bed. 



Double English violets. Marie Louise, Lady Camp- 

 bell, and others. For plant-lice and general fumiga- 

 tion fifteen-hundredths of a gramme of 98 per cent, 

 cyanide of potassium for each cubic foot of space is 

 required. The exposure, if made according to direc- 

 tions, will not hurt the plants in any stage of growth. 

 The gas has been used on a large scale in fumigating 

 violets for the past three years with the greatest sue- 



