18 BULLETIN 828, U. S. DEPARTMENT OF AGRICULTURE. 



case of wilt occurred throughout the summer of 1916 in the cucum- 

 bers growing in this artificially infected soil in any of the 50 cages, 

 although, as in the preceding season, the disease was abundant on 

 the plants outside the cages. 



At Giesboro Point, D. C, a second experiment, using 20 similar 

 cages, was carried out during 1916 on land planted to Hubbard 

 squashes the preceding season. Wilt was very prevalent in these 

 vines during the fall of 1915, as verified by personal observations and 

 by pure-culture isolations. Many hills bearing wilted vines were 

 marked at this time, and 12 of the cages were set directly over such 

 hills. A wire netting slightly coarser (16 meshes to the inch) than 

 that used in the Long Island experiments was employed for these 

 cages, with the result that some of the smaller beetles, especially of 

 the second brood, gained entrance. Until the first of July all of the 

 cages were gone over every day except Sunday and any beetles or 

 gnawed leaves found within were removed. Wilt in this vicinity 

 first appeared on June 3 in four near-by fields not in cucurbits the 

 preceding season and on June 13 in the cucumbers around the cages. 



On July 5, over a month after the first appearance of wilt in this 

 vicinity, a gnawed leaf which had been overlooked in one of the 

 cages began to wilt around the points of injury. With the appear- 

 ance of many small beetles of the second brood in July it became 

 impossible to keep them entirely out of all the cages. On that 

 account, after July 25, wilt occurred in single plants in 4 other cages 

 out of the 20. In all these cases striped cucumber beetles had gained 

 entrance, and the first leaves to wilt were those showing beetle in- 

 juries. There was no infection from the soil in any case, but direct 

 and positive evidence of infection from cucumber-beetle injuries 

 and absence of infection in the absence of such injuries. 



SPRING SEQUENCE OF WILT. 



In addition to the cage experiments during the early part of the 

 season of 1916, a complete record was kept of the first appearance 

 and spread of bacterial wilt of early cucurbits in all the field and 

 garden plats in these two localities. 



At East Marion, Long Island, the area selected comprised the land 

 between Long Island Sound and Greenport Harbor and extending 

 about 2 miles east and west. (Fig. 1.) No wild cucurbits occurred 

 within at least 10 or 15 miles of this locality. 1 



A careful inspection on June 8, 9, and 22 of all cultivated cucurbits within this area 

 gave no evidence of wilt. 



The first wilt of the season was found on June 29 on a cucumber plant (fig. 1) in our 

 experimental Field IV, planted May 24, 1916, and not in cucurbits the preceding 

 season. The plants were just breaking through the ground on June 5, but on account 



i Rand, F. V., and Enlows, Ella M. A., 1916. Op. cit., footnote 2, p. 419. 



