PRESOAK METHOD OF SEED TREATMENT: A MEANS 

 OF PREVENTING SEED INJURY DUE TO CHEMICAL 

 DISINFECTANTS AND OF INCREASING GERMICIDAL 

 EFFICIENCY 



By Harry Braun ' 



Scientific Assiitant, Laboratory of Plant Pathology, Bureau of Plant Industry, United 

 States Department of Agriculture 



INTRODUCTION 



The widespread use of formalin, copper sulphate, and other germicides 

 in seed treatment for the control of seed-transmitted diseases is generally 

 attended by decreased and retarded seed germination. Pathogens on 

 the seed coats, present as dry bacteria, fungus spores, or dormant myce- 

 lium, are usually in a resting stage and as such require the use of dis- 

 infectants in a fairly strong concentration — i to 80 for copper sulphate 

 (CuSOJ and i to 200 or i to 320 for formalin (CH,0) — which often act 

 very detrimentally on the germinating seed. Even much weaker solu- 

 tions — I to 200 for copper sulphate and i to 400 for formalin — exhibit 

 retarding and killing effects when used on wheat. The use of lime after 

 copper sulphate, while beneficial to some extent, does not entirely prevent 

 seed injury, nor has the detrimental effect of formalin been so far fully 

 counteracted. The economic importance of the annual loss of grain due 

 to seed treatment is such that during the recent war it occasioned an 

 elaborate series of tests of standard grain disinfectants by the War 

 Emergency Board of the American Phytopathological Society. 



In fact (j)2— 



the difficulty of avoiding injury to the seed from treatment that is too severe or from 

 improper drying after treatment has undoubtedly had more influence in preventing 

 the general spread of the practice of disinfecting seed grain than has the cost of ma- 

 terials or the difficulty of the treatment itself. 



In the course of investigations on the blackchaff bacterial disease of 

 wheat (5, 6, 7, 8), under the direction of Dr. Erwin F. Smith, a new 

 treatment (/) of seed wheat with formalin and copper sulphate has been 

 discovered whereby seed injury due to these disinfectants is either en- 

 tirely eliminated or is reduced to a negUgible minimum, while at the same 

 time the bacteria are rendered more susceptible to the action of the dis- 

 infectant. The result has been accomplished by a correlation of two 



1 The author wishes to acknowledge his indebtedness to Dr. Erwin F. Smith for helpful criticism and 

 advice throughout the course of this investigation. 

 ' Reference is made by number (italic) to " Literature cited," p. 392. 



Journal of Agricultural Research, Voi. XIX. No. 8 



Washington, D. C. Ju'v '5. 1920 



up Key No. G-198 



(363) 



