Vegetable and Field Crops 177 



of several spots. The spots soon become brown, and the 

 central part turns ashen-white and is seen by the aid of a 

 hand lens to bear numerous hyphge. The leaves may bear so 

 many spots as to appear as though scorched, and often death 

 results to the entire plant. 



The disease spreads most rapidly in damp, warm weather. 



Market! difference in varietal resistance was reported by 



Fig. 96. — Early-blight of celery. Original. 



Tracy as early as 1885, the Boston Market and Golden 

 Heart suffering much, while the White Plume was but slightly 

 injured. 



All plants showing a trace of disease should be rejected. 

 Healthy plants from infected lots may with advantage be 

 dipped in Bordeaux mixture to cleanse them of adhering 

 spores. Spraying with ammoniacal copper carbonate or 

 Bordeaux mixture is effective. Treatment should be begun 

 before the disease appears, i. e., in the seed bed, and con- 



