May IS, 1915 Seedling Diseases of Sugar Beets 149 



From what has been said regarding sources of infection, it appears 

 that ordinary attention to rotation should eliminate danger from soil 

 infection, but that all seed at present available is heavily infected. The 

 only hope of control therefore lies in one or more of three alternatives: 

 (i) The natural resistance of the beet to the attacks of the fungus, (2) 

 seed treatments, (3) the production of disease-free seed. 



From the facts that the period of infection with Phoma betae is 

 normally confined to a relatively short period in the seedling stage and 

 that infected plants frequently throw off the attack, proper attention to 

 cultural conditions would seem to offer hopeful prospect of control. 

 European experience has demonstrated the value of such methods. 

 Indeed, some prominent agriculturists have denied the pathogenicity of 

 Phoma betae because of their success in preventing damping-off and root 

 sickness by proper cultivation and fertilization. From this they have 

 argued that the cause lies in unfavorable cultural conditions rather than 

 the presence of parasites. The truth undoubtedly is that unfavorable 

 environment is a predisposing cause which so weakens the beet that it is 

 unable to compete successfully with the fungus. When planted in good 

 soil, which has been well prepared and suitably fertilized, the seed germi- 

 nates promptly and the young plants pass rapidly through the period of 

 danger. Early cultivation at this stage to insure proper aeration of the 

 roots is beneficial. The studies upon control by means of cultural 

 methods and fertilizers demonstrate the value of properly prepared soil 

 and thorough cultivation promptly after the seedlings come through the 

 ground. There is no doubt that frequently an infected stand may be 

 saved in this way. In Europe the use of phosphoric acid and potash 

 has given good results*. The question of soil reaction has also been found 

 very important. Applications of lime on certain types of acid soil result 

 in 'almost complete control. This may also prove to be the case in 

 America, but the point can be determined only by local experiment. 



As has already been said, the only method of seed treatment which has 

 given satisfactory results in pot experiments is seed pasteurization. 

 Experimental work to test the efficiency of this method in field practice has 

 been attempted. It is not believed that a method of treatment as 

 difficult to carry out as pasteurization will prove useful except in the 

 hands of experimentalists and for experimental purposes. It is apparent 

 that seed must be treated in small lots and with extreme care in order 

 to secure the desired result. If temperatures much above 60° C. are 

 employed, the injury to the seed becomes serious. Temperatures below 

 60° are ineffective. The substitution of one treatment for two is like- 

 wise unsuccessful. Attempts to apply the treatment to samples of seed 

 of even 5 pounds have not been altogether satisfactory, but appear to 

 hold the fungus in check. 



One experiment in seed treatment carried out under field conditions 

 where epidemic development of root sickness has annually occurred for 



