20 BULLETI153" 1029, U. S. DEPAETMEI:^T OF AGKICULTUKE. 



always be relied upon to yield successful control. This point will be 

 emphasized further by data from commercial trials presented in the 

 following pages. 



RESULTS WITH TREATED SEEDS IN COMMERCIAL FIELDS. 



To determine the practical value of cabbage-seed treatment, several 

 lots of Gommerciall}'- grown seed, varying in weight from 2 to 400 

 pounds, were treated before distribution in 1918 and 1919. All the 

 seed except lot No. 14^18 was grown in the vicinity of Racine, Wis., 

 and most of it was kept under the writer's observation. Varying 

 amounts of black-leg prevailed on the seed plants, but in no case was 

 a high percentage of pods infected. As noted before, the most seri- 

 ously diseased lot. No. 2-18, when tested in the greenhouse showed 

 primary infections on approximately 2 per cent of the plants. Un- 

 less otherwise stated, the seed was disinfected by the writer. It should 

 be noted that in the cabbage sections where these observations were 

 made, seed is sown in open beds about the first week of May, while 

 transplanting is done as a rule between June 15 and July 5. Wliere 

 possible, a survey of the seed beds was made before transplanting 

 was begun, and final notes were taken in representative fields at the 

 end of the season. 



KESULTS IN 1918. 



All of the fields under observation in 1918 were located at Eacine, 

 Wis., and were grown from seed which had been treated with a 1 : 256 

 formaldehyde solution for 30 minutes. Seed beds were sown about 

 April 25. When a survey of the beds was made on June 14 the dis- 

 ease was alread}" quite prevalent. Most of the transplanting was 

 done between June 15 and June 30. There was no reason to believe 

 that infection had originated otherwise than by way of the seed, since 

 most of the beds were on soil new to cabbage or on which the crop 

 had not been grown for several years. The rainfall records for this 

 section (fig. 1) show that previous to June 14 the weather had been 

 favorable for the rapid spread of the disease from primary centers. 



As a result of the early spread of the fungus in the seed bed, the 

 disease became very destructive as the season progressed. This de- 

 velopment was confined largely to the home-grown seed, in spite of 

 the fact that this had all been treated. A summary of the amount of 

 disease in five representative fields at the end of the season is given 

 in Table VIII. A typical field grown from this seed as it appeared 

 at the end of the season is shown in Plate I, A. It was clear from 

 this season's results that treatment with a 1:256 formaldehyde solu- 

 tion does not successfully control the disease when sufficient rainy 

 weather prevails to bring about the dissemination of the fungus in 

 the seed bed. 



