214 Journal of Agricultural Research voi. xv, no. 3 



INSECTS 



The hypothesis that the bacteria may overwinter in or on the bodies of 

 insects is here mentioned because it might seem plausible in view of the 

 theory advanced with good evidence by Rand and Enlows {13) to 

 account for the overwintering of the organism causing the wilt of cucur- 

 bits. No dependent relationship, such as has been found to exist between 

 the wilt and cucumber beetles, has been observed in the case of angular- 

 leaf spdt. Field observations in 191 6 furnish some good negative evi- 

 dence relative to the insect-overwintering theory. In one vicinity near 

 Madison six cucumber fields on "new" land planted with seed from one 

 source became diseased early, while four fields (planted with seed of a 

 different source) on or very near land which had previously been planted 

 with cucumbers did not develop the disease early. The early brood of 

 beetles was fully as abundant on the four latter fields as on those six 

 that became diseased early in the season. 



SEED 



The observations which formed the preliminary basis for the seed- 

 overwintering theory have been printed before (6), but for the sake of 

 bringing together all the pertinent evidence may be here repeated. In 

 June, 1 91 5, angular-leaf spot was observed in abundance in a field south 

 of Portsmouth, Va. The plants were developing their fifth and sixth 

 leaves at the time. The field was on newly cleared land, surrounded by 

 woods and at least 3 or 4 miles from the nearest cucumber patch. The 

 evidence pointed strongly to the introduction of the organisms with the 

 seed. 



The developments in the fields near Madison in 191 6 gave further 

 evidence that the organisms are introduced with the seed. The six 

 experimental fields previously mentioned were all on land which had not 

 been planted to cucumbers for at least three years. Angular-leaf spot 

 appeared on seedlings in all six of these fields, and in three of them it 

 was noted on the cotyledons. In the case of the four commercial fields 

 near by which were planted with seed from another source the disease 

 did not appear at all in one and not until late in the season in the other 

 three. This evidence so strongly indicated that the bacteria live over 

 winter on the seed that it seemed worth while to study the matter in the 

 commercial seed fields. Accordingly the writer visited a large seed- 

 producing center in Iowa and Dr. M. W. Gardner, because of his interest 

 in the question in relation to cucumber anthracnose, visited a seed farm 

 in Ohio. In one of the seed fields in Iowa the disease was widespread 

 and, according to a hasty estimate, 25 per cent of the fruits were attacked. 

 Dr. Gardner found spots on the fruits in the Ohio fields which he was 

 reasonably sure were due to the angular-leaf spot organism. 



