STUDIES IN GREENHOUSE FUMIGATION WITH 

 HYDROGANIC ACID 



Temperature and Moisture as Factors Influencing the Injury of 

 Plants During Fumigation." 



William Moore. *••= 



INTRODUCTION. 



A cursory review of the literature dealing with the fvmiigation 

 of greenhouses with hydrocyanic acid reveals a great diversity of 

 opinion among entomologists as to the most successful doses to be 

 used, and the influence of various physical factors in the success 

 of the fumigation. Although hydrocyanic acid fumigation has 

 been used in greenhouses since 1899 (1) our knowledge of the 

 conditions necessary for successful fumigation although largely 

 empirical, has brought about its general use for certain insects and 

 crops, such as red spider on violets and white fly on tomatoes and 

 cucumbers. 



The most important question to be answered, l^efore taking up 

 an examination of the influence of any factor in increasing or de- 

 creasing the injurv to plants during fumigation, is the manner in 

 which the gas penetrates the tissues of tlie plant. 



The Penetration of the Gas Into Plants. 



Woods and Dorsett (1) considered that hydrocyanic acid gains 

 entrance to the plant l)v wav of the stomata while Stone (2) 

 considers from his work that susceptibility to injury is due more 

 directly to the condition of the tissue of the plant rather than the 

 open or closed condition of the stomata. Conditions which tend to 

 develop a thin cuticle were found to favor injury during fumigation. 



The following experiment was conducted to determine if hydro- 

 cyanic acid would cause the stomata of the plant to close during 

 fumigation. Peas, lettuce and geraniums were fumigated with 

 hydrocyanic acid under a bell jar in the bright sunlight. Similar 

 plants were placed under a bell jar in the sunlight as a control. 

 Strips of the epidermis of the plants were obtained after dift'erent 

 exposures, and dehydrated with absolute alcohol, stained, mounted 



♦Published with the approval of the Director as Paper No. 68, of the Journal Series of the 

 Minnesota Agricultural Experiment Station. 



**The author wishes to express his appreciation of the assistance of O. G. Babcock, S. Mar- 

 covitch, and S. A. Graham in carrying out the fumigations and experiments upon which this 

 paper is based, and to I. J. Williman, of the Division of Chemistry, for assistance in chemical 

 analysis, etc. 



