34 
BULLETIN 828, U. S. DEPARTMENT OF AGRICULTURE. 
3:30 
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FIRST SIGNS OF WILT 
WILT OF FIRST LEAF 
WHOLE PLANT WILTED 
1 
flg 
(0 
all, in 15 to 20 days after inoculation (fig. 8). However, in 26 out 
of the 51 sets of inoculations the plants all recovered after partial 
wilting. It will be noted that the first signs of the disease and wilting 
of the first leaf were only a little slower in appearing than in cucumber, 
but in general a much longer time elapsed before the whole plant 
became involved. A far greater percentage of recovery was exhibited 
than in cucumber. 
Field records during 1916 in the spray plat at East Marion, Long 
Island (fig. 1, Field Ha), showed that among the cucumbers where 
wilting of the first leaves appeared on July 12 the larger number of 
plants had completely succumbed six days later (July 18). The 
vines at this time were 1 to 2 feet in length, which was approximately 
the size of those used 
in the greenhouse in- 
oculation tests above 
noted, and it will be 
seen at once that the 
period between the 
wilting of the first 
leaves and the total 
wilting of the plant 
corresponds very 
closely under the field 
conditions and the 
greenhouse con- 
ditions. 
Of the plants which 
showed wilting of the 
first leaves on July 18 
the larger number had completely wilted 1 1 days later, while of those 
with first wilt on July 29 the larger number lived for 17 days longer. 
Complete records of later infections could not be obtained, on ac- 
count of the appearance of downy mildew. 
As would be expected, the larger the plant the longer the period of 
time elapsing between initial and total wilting. However, the two 
are not directly proportional, since in the older plants the absolute 
progress of the disease is slowed down through some relation to the 
condition of senility in the host. (Cf. pp. 31 and 32.) 
DISTRIBUTION OF BACTERIAL WILT. 
Bacterial wilt of cucurbits was reported by Dr. Erwin F. Smith 1 
as occurring (fig. 9) in Canada, Massachusetts, Vermont (?), Rhode 
Island, Connecticut, New York, New Jersey, Delaware, Maryland, 
District of Columbia, Virginia, West Virginia, Pennsylvania, Ken- 
CQ 
2 
10 20 
Number of pays 
Fig. 8. — Diagram showing the progress of wilt in 51 inoculation tests 
on squash (mostly the White Bush Scallop variety), with two or 
more plants to a test and in all using 21 different isolations of 
Bacillus tracheiphilus. 
i Op. cit. ; p. 209-211. 
