64 BULLETIN 727, U. 8S. DEPARTMENT OF AGRICULTURE. 
has been isolated from soil under diseased plants and from surface 
‘drainage water after rains. 
The disease is especially destructive in certain fields where arti- 
ficial overhead watering is practiced. Convincing evidence of hand 
dissemination by workmen during the process of culling watermelon 
fields has been secured. : 
The mode of origin of the disease in new fields in original centers 
and its appearance in only the fields planted with seed from certain 
sources suggest that the fungus is introduced with the seed. 
Anthracnose has been found prevalent in seed fields on the fruits. 
The process of seed extraction affords ample opportunity for whole- 
sale surface contamination of seed. The cellulose ‘‘hairs’”’ on the 
seed coat would afford lodgment and protection to spores. Frag- 
ments of tissue from fruit lesions have been found among and ad- 
herent to seeds. No evidence of the presence of dormant mycelium 
within seeds removed from beneath deep fruit lesions has been 
secured. 
Numerous laboratory and greenhouse tests have failed to prove 
the presence of infectious material on commercial seed. With 
inoculated seed, diseased seedlings result. 
Extensive field tests with treated and untreated seed, while incon- 
clusive, indicate that the fungus is carried with the seed. 
Convincing evidence that the fungus overwinters in the field has 
been accumulated. The disease recurs annually in certain localities 
and not in others. In experimental fields planted with treated seed, 
the disease reappeared in those which bore a diseased crop the 
‘previous year. In extensive field tests with treated seed, 90 per 
cent of the cases of anthracnose may possibly be thus explained. It 
has been proved that the fungus overwinters in diseased-vine débris 
buried in soil. 
Bordeaux sprays check but do not prevent the spread of the 
fungus. The lower epidermis of a sprayed leaf is unprotected. 
Spraying may be advisable in the melon, slicing-cucumber, and 
seed-cucumber crops, but is not practicable in the cucumber-pickle 
srowing industry. 
It.is believed that surface disinfection of the seed will eliminate 
the infectious material. For this purpose, immersion in mercuric 
chlorid, 1 to 1,000, for 5 minutes has been found effective and prac- 
tically noninjurious. Disease-free seed may also be secured from 
disease-free seed fields, and possibly by the use of old seed. 
The use of disease-free seed and a proper crop rotation to insure 
clean soil are recommended as control measures. 
