26 BULLETIN 1029, U. S. DEPARTMENT OF AGRICULTURE. 



utes. This occurred under weather conditions favorable to the 

 disease, owing to frequent rains. 



(8) In 1919, in the same locality, under dry weather conditions, 

 the disease was quite effectively controlled by seed treatment, soak- 

 ing in 1 : 500 mercuric chloricl for 30 minutes, followed by rinsing 

 in clean water. At Shiocton and Appleton, Wis., where longer and 

 more frequent rainy periods prevailed between the appearance of 

 primary centers and transplanting, serious ej)iphytotics developed 

 from the same lots of seed as used in the Racine district. It was 

 thus shown that even this strong treatment was insufficient to con- 

 trol the disease effectively when climatic conditions favored the 

 rapid spread of the fungus from primary centers. 



(9) Since treatment reduces the number of primary centers and 

 retards their development somewhat and since it is also a preven- 

 tive against seed-borne black-rot organisms, it should be recom- 

 mended. The limitations to success in the control of black-leg, how- 

 ever, should be recognized. 



(10) Trials have developed the fact that different lots of cabbage 

 seed may vary considerably in their relative susceptibility to injury 

 from seed-disinfection treatments. Stronger treatment than a 1 : 256 

 or 1 : 240 solution of formaldehyde or a 1 : 1,000 sokition of mercuric 

 chlorid for 30 minutes followed by rinsing is unsafe for general use. 

 Of these two treatments, the mercuric chlorid seems to be slightly 

 superior in eradicating the fungus. It is true, hoAvever, that many 

 lots of seed will stand much more severe treatment, especially with 

 mercuric chlorid, but in the event of such treatment preliminary 

 tests should always be made. 



(11) In view of the limitations of treatment in controlling black- 

 leg special attention should be given to securing disease- free seed. 



