228 DISEASES OF ECONOMIC PLANTS 



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- 

 tinued at ten-day to fourteen-day intervals, throughout the 

 growing period. All spore-bearing refuse should be burned. 



Leaf spot, late blight, septoriose (Septoria Petroselini 

 Desm. var. Apii Br. & Cav.). — In Italy late blight was 

 first reported in 1890; in the United States in 1891. 

 A loss of 1950 carloads and a money loss of $550,000 was 

 estimated in California in 1908. 



In its beginning it consists of leaf spots very like those 

 of the last disease, though more irregular and indefinite in 

 boundary. In later stages, the infection of the leaf becomes 

 general, numerous black pycnidia are scattered upon all 

 parts of the leaf and even upon the l)lanched petioles, 

 which through their unsightliness injure the salability of 

 the crop. In extreme cases wilting of the leaves and de- 

 struction of the plant follows. After the celery is put 

 in storage the disease may still progress and do great 

 damage, rotting off the leaves and forcing early marketing. 

 This disease is often found in the seed bed, and is prob- 

 ably carried by the seed, since the pycnidia are abundant 

 upon the seeding stalks and fruit. If the disease has 

 been troublesome in preceding years, the plants in the seed 

 bed should be sprayed with Bordeaux mixture as soon 

 as they are above ground, and once or twice a week there- 



