UNITED STATES DEPARTMENT OF AGRICULTURE 



J^^'^L 



i BULLETIN No. 513 



Contribution from Bureau of Entomology. 

 L. O. HOWARD, Chief. 



Washington, D. C. 



March 10, 1917 



FUMIGATION OF ORNAMENTAL GREENHOUSE 

 PLANTS WITH HYDROCYANIC -ACID GAS. 



By E. R. Sasscer, Collaborator, and A. D. Borden, Scientific Assistant. 



CONTENTS. 



Introduction 1 



Equipment necessary for fumigation 2 



Preparation of house for fumigation 3 



Method of computing the cubical contents of 



even and three-quarter-span greenhouses.. 4 



Time for fumigation 4 



Chemicals required for fumigation 5 



Determining the amount of cyanid to be used. 5 



Chemical formula to be employed 6 



Mixing the chemicals 7 



Number of generators to be employed 7 



Exposures 7 



Ventilation after fumigation 8 



Eflects of weather conditions on fumigation . . 8 



Advisability of a fumigation box 9 



How insects are disseminated from house to 



house 9 



Cost of hydrocyanic-acid gas fumigation 10 



Precautions H 



Plants and insects fumigated in greenhouses. . 11 

 Plants and insects fumigated in fumigation 



box 18 



Conclusion 20 



INTRODUCTION. 



Hydrocyanic- acid gas, if intelligently employed, is one of the 

 cheapest and most efficient methods of controlling thrips, aphids^ 

 white flies, and various scale insects on plants grown under glass. 

 That this method of control has not been generally adopted is no 

 doubt owing to the deadly poisonous nature of the gas if inhaled, its 

 disastrous effect on tender plants if improperly used, and the pre- 



NoTE. — -Hydrocyanic-acid gas was first used against greenhouse pests in 1895 by Messrs. 

 A. F. Woods and P. H. Dorsett (see Circular No. 37, Bureau of Entomology, U. S- 

 Department of Agriculture) in an effort to destroy insects on diseased plants under 

 observation. Subsequently others have employed the gas in greenhouse fumigation, but 

 with varying success, largely because of inexperience and improper methods of procedure. 

 In the earlier experiments in greenhouses conducted by the Bureau of Entomology the 

 senior author was assisted by Mr. H. L. Sanford, of the Federal Horticultural Board, 

 and by Messrs. Eugene May, W. R. Lucas, and Charles Keller, of the Bureavi of Plant 

 Industry. The spelling of the botanical names used in this publication has been verified 

 by Messrs. P. L. Ricker and H. C. Skeels; 



Caution. — Hydrocyanic-acid gas is colorless and is one of the most deadly poisonous 

 gases known. It has an odor much like that of peach pits. In case of accidental inhala- 

 tion of the gas, the person affected should ie kept in the open air and required to walk 

 to increase respiration. 



71777°— Bull. 513—17- 



