42 The Bulletin. 



CABBAGE DISEASES. 



By F. L. Stevens, 



Botanist and Pathologist of the North Carolina College of Agriculture and 

 Mechanic Arts, West Raleigh, N. C. 



A very brief account is given below of the most important cabbage 

 diseases with suggestions as to their treatment. 



Blach Rot: The leaves first show signs of disease upon their edges 

 by a blackening of the veins. This blackening rapidly extends down 

 the veins toward the stalk and thus up other veins and eventually 

 throughout the plant. The diseased leaves soon turn yellow and wilt 

 and eventually fall to the ground. The disease may always be recog- 

 nized with certainty by the black veins which are especially conspicu- 

 ous in cross sections of the leaf stem. The disease is caused by bacteria 

 which enter through small holes (water pores) at the leaf edge. These 

 bacteria may remain in infected fields for years, may be spread by 

 manure which has received infected trash, and may also be carried 

 upon seed. ISTo remedy is known for fields after they are once infected, 

 except a long crop rotation, avoiding all susceptible plants. To avoid 

 introducing the disease on seed it is well to soak the seed in corrosive 

 sublimate one part, hydrochloric acid two parts, and water 1,000 parts, 

 soaking for fifteen minutes. The disease now practically precludes suc- 

 cessful cabbage growing in many sections of the State, to which it has 

 come upon seed. 



Cluh Root: In this disease the root becomes very greatly swollen 

 and distorted and the plant is so weakened as to be valueless. This is a 

 germ disease whose causal organisms remain in the soil from year to 

 year, therefore, fields which have borne a diseased crop should not be 

 planted again to susceptible crops without a long intervening rotation. 

 The disease may be spread to new fields by infected refuse or manure 

 which has received such refuse. Especial care should be taken to use 

 uninfected soil for the seed bed and to avoid infecting the seed bed with 

 manure or refuse. In some sections it has been found profitable to use 

 air-slaked stone lime, 75 bushels per acre, applied some weeks before 

 planting. 



Downy Mildew: Characteristic downy white patches appear on the 

 lower surface of the leaves. The corresponding areas as seen from above 

 turn yellow. This disease is seldom serious in the field but is occasion- 

 ally damaging in the seed bed. The diseased plants should be sprayed 

 with Bordeaux mixture. After setting all diseased plants remaining 

 in the bed should be destroved bv fire. 



•This brief article was prepared by Dr. Stevens at the request of the author of this Bulletin because 

 many growers will desire to have some knowledge of the diseases available in the same Bulletin which 

 discusses the insects. The grower should remember, however, that the two subjects involve entirely 

 separate fields of study. Plant diseases come under the study of the botanist, while the insects are 

 studied by the entomologist. 



