July IS, 1920 



Presoak Method of Seed Treatment 



381 



EFFECT OF SIX HOURS PRESOAKING FOLLOWED BY FORMALIN I TO 320 AND COPPER 

 SULPHATE I TO 80 ON ARTIFICIALLY INFECTED WHEAT SEEDS PLANTED IN THE 

 SOIL UNDER FIELD CONDITIONS 



Several field tests were made v/ith seeds of Currell, China, and Dietz 

 varieties artificially infected with blackchaff bacteiia, dried, and treated 

 with formalin i to 320 and copper sulphate i to 80, after a presoaking of 

 six hours. The percentages of infection in the young seedlings two to 

 three weeks after planting are given in Table IX. 



Table IX. — Effect of presoak method of treatment on inoculated wheat seeds under field 



conditions 



" From Kansas. 



'' From Colorado. 



<■ From Montana. 



Bacterial infection was prevented to a very marked degree in the 

 treated seeds. The controls, infected with five isolations of Bacterium 

 translticens var. u^ndulosum from different localities, showed from 69 to 

 95 per cent infection, considerably more than would usually occur in 

 naturally diseased seed, owing to the heavy artificial inoculation and 

 brief drying period before planting. Infection of these seeds, heavily 

 inoculated as they were, v/as reduced from o to 1.5 per cent by the pre- 

 soak method, used with both formalin and copper sulphate. The appli- 

 cation of this method, then, to the control of blackchaff on the farm is 

 evident. The only doubt that can be entertained is in cases where the 

 bacteria have penetrated the seed coats. Fortunately, in most such 

 cases at least, the seeds are more or less shriveled and of light weight so 

 that they may be screened out in advance of treatment. 



