lOO Report of the Botanist of the 



From the plants on the treated half-acre all diseased leaves 

 were removed once a week on the following dates: July 22 and 

 29; August 5, 12, 19 and 26; September 2, 9 and 16. The total 

 amount of time required to make these nine treatments on one 

 half-acre was 46^ hours for one man. 



At the time of the first treatment, July 22, it was estimated 

 that 33 per ct. of all the plants were showing more or less leaf 

 infection. From this time until well into September the disease 

 continued active. At each treatment there were multitudes of 

 diseased leaves to be found notwithstanding every diseased leaf 

 had been removed one week previous. In spite of all that could 

 be done large numbers of new infections continued to appear. 

 For a time every plant found to be afifected in the stem was 

 removed as in previous experiments; but this was soon aban- 

 doned as it was plain that it would result in a serious depletion 

 of the treated plat. Although the disease was so abundant that 

 on the check plat scarcely a single plant wholly free from it could 

 be found by September 2, only a few plants were completely 

 ruined by it, and the attack is to be regarded as only a moderate 

 one.^ This view is supported by the yield on the check plat 

 which was at the rate of over ten tons per acre. 



The 27 rows of Henderson's Succession were harvested Octo- 

 ber 13 and the 27 rows of Danish Ball Head, November 8. The 

 results are shown in the following table: 



9 Black rot is not so certainly fatal as one might infer from the literature of the 

 subject. A good yield of cabbage may often be obtained from fields in which almost 

 every plant shows more or less infection. This may be true even when the infec- 

 tion occurs early in the season. Plants infected within a month after transplanting 

 may live to produce marketable heads of good size. Even plants in which the 

 disease has gained access to the main stem often produce marketable heads and the 

 removal of such plants causes unnecessary loss. The rapidity with which the disease 

 progresses within the plant is greatly influenced by weather conditions and the con- 

 dition of the plant. 



Black rot appeared abundantly in many fields in the vicinity of Geneva about 

 August I, 1899, but drought during the next two months decreased the succulence 

 of the plants and seemed to check the progress of the disease. 



During the season of 1902 there was an abundance of moisture, but the tempera- 

 ture was unusually low, and while nearly every plant in our experiment field con- 

 tracted the disease few were destroyed. 



