SEED DISINFECTION BY FORMALDEHYDE VAPOR 



[PRELIMINARY REPORT] 



By Cecil C. Thomas 



Pathological Inspector, Federal Horticultural Board, United States Department of 



Agriculture 



INTRODUCTION 



The continual introduction of plants by the Department of Agriculture, 

 chiefly by means of seeds, from all parts of the world, and the constant 

 danger of allowing little-known or serious diseases to enter thereon, 

 emphasize the necessity for a study of the methods of seed disinfection. 

 There are few data on this subject except in the case of cereals and for 

 a small number of seeds used in physiological experiments. 



The pathological inspectors of the Federal Horticultural Board have 

 encountered many difficulties in treating hundreds of lots of seeds of 

 \videly varying types and quantities with the various liquid treatments 

 in common use. Most of the treatments recommended and used at the 

 present time require dipping or soaking in a water solution of some 

 fungicide or germicide. The seeds, therefore, remain wet for a longer 

 or shorter period, depending on the treatment given and the method of 

 drying. 



Some seeds like wheat and rye absorb water slowly and can be dried 

 without much injury, while seeds like the various members of the mustard 

 family absorb water very readily and with even a very brief treatment 

 swell sufficiently to break the seed coat and allow the cotyledons to fall 

 apart, thus destroying the seed. 



Light seeds such as are found in many of the grasses present another 

 problem for the wet treatment. It is very difficult to give them anything 

 like a uniform treatment because of the difficulty of wetting them and 

 keeping them under the liquid. Seeds such as flax, which have a muci- 

 laginous covering, present still another difficulty for wet treatments. 



The large number of shipments and the great variety of seeds passing 

 through the quarantine inspection house of the Federal Horticultural 

 Board, United States Department of Agriculture, that need to be treated 

 render desirable the adoption of a method of treatment which will 

 ob\nate wetting and drying. An attempt, therefore, is being made to 

 develop a treatment of this type with formaldehyde vapor. While it is 

 far from being perfected, it seems desirable to make a preliminary report 

 on some of the results obtained. 



Journal of Agricultural Research, Vol. XVII, No. t 



Washmgton, D. C. Apr. is. 1919 



rr Key No. O— 3 



(33) 



