ANTHRACNOSE' OF CUCURBITS. 43 



While rain water may be the usual requisite for infection, it is 

 evident that other conditions may also permit its occurrence. 



DISSEMINATION BY INSECTS. 



While insects may possibly act as agents of dissemination, there 

 is no indication that they are at all important in this capacity. It 

 has been previously noted that the striped cucumber beetles often 

 feed on the tissue about the margins of leaf lesions, and it is evident 

 that infectious material might be subsequently transported by these 

 beetles. 



A few tests were made to determine what part insects might play 

 as agents of disease transport. On August 11, 12 striped and 12 

 spotted beetles were collected from anthracnose centers in field 2 

 and about 10 of each species were introduced under two cheesecloth 

 cages covering plants in field 1. Drainage-water infection of the 

 plants under the cages in this field ruined this test. On September 

 6 three spotted beetles were collected in sterile test tubes from dis- 

 eased plants and each beetle was placed in 50 c. c. of sterile water. 

 Plates poured from this wash water yielded no colonies of the anthrac- 

 nose fungus. 



No proof was obtained, therefore, that insects spread the disease, 

 and observational evidence has not tended to implicate them. 



DISSEMINATION BY CULTURAL PRACTICES. 



Since the spores may occur abundantly in the soil, it seems quite 

 possible that the disease might be spread during the processes of cul- 

 tivation. For this disease, unlike bean anthracnose, observation has 

 not yielded indications of this type of dispersal. 



The process of picking the cucumber crop grown for pickles would 

 seem to afford a very fruitful means of disease dispersal. Since this 

 process is repeated at least four times a week and involves consider- 

 able handling of the vines, it may contribute much to the spread of 

 the anthracnose along the row from an old center. This is especially 

 true if picking is done when the vines are wet with dew or rain. At 

 one of the coldframe farms near Norfolk where the disease was very 

 serious, it was found that picking was done early each morning, when, 

 no doubt, dew was on the vines. 



The occurrence of more or less isolated leaf lesions here and there 

 among the leaves is taken as evidence of this type of dissemination. 

 From these lesions as a source, new centers of infection may develop. 

 Such infection differs from the type produced by drainage trans- 

 port in that, in the latter, the infection is continuous along the row 

 from the old center. 



Among watermelons, quite conclusive observational evidence was 

 secured relative to the agency of man in spreading anthracnose. In a 



