8 
BULLETIN 1288, U. S. DEPARTMENT OF AGRICULTURE 
distributed in the bottom of the furrow as the land was plowed in 
the fall; on the others they were scattered on the surface. Xo fur- 
ther treatment was given until spring, when all plats were disked 
and planted with tomatoes. Cultivation was delayed until the plats 
became weedy, in order to prevent bringing in spores from other 
fields. The results noted on July 11 are recorded in Table 3. 
Table 3. — Results of experiments to control tomato leaf-spot oy thoroughly 
plowing under the dead tomato vines in the fall 
[Infected tomato stems and leaves distributed in the fall; land disked in the spring; examination of 
results on July 11] 
Character of the plats 
Plowed plats: Infected ma- 
terial distributed in the 
bottom of the furrow 
Control plats: Infected ma- 
terial distributed on the 
surface 
Total 
number 
of plants 
Number 
of plants 
infected 
Plants 
infected 
(per cent) 
Total 
number 
of plants 
Number 
of plants 
infected 
Plants 
infected 
(per cent) 
Highland.. . . . ... 
75 



97 
86 
23 
88.6 
! 
1 23.2 
> Water flowed over this plat in the spring and deposited a layer of mud which covered most of the old 
tomato stems and leaves. 
On July 11 no tomato plants were infected on the plowed plats, 
but 88.6 and 23.2 per cent were infected on the controls. A layer 
of mud deposited in the spring on the control which contained 
23.2 per cent of infected plants apparently reduced the proportion 
of Septoria. Late in the season there was a little infection by Sep- 
toria on the plowed plats, but this was after they had been culti- 
vated several times and the fungus had apparently been carried 
in by men and teams, or possibly by insects from other tomato 
fields. However, the amount of Septoria on these plats even at 
the end of the season was relatively small. These results agree 
with those obtained by the use of soil in tube cultures and seem 
to indicate that Septoria may be largely prevented from over- 
wintering by thoroughly plowing under the dead tomato vines in 
the fall. Even if the plowing were delayed until early spring it 
might possibly be made effective by thoroughly turning under 
all the tomato vines, harrowing the surface lightly, and plant- 
ing the land to a noncultivated crop. Planting all tomatoes on 
fall-plowed land would also help control leaf-spot, or blight, as 
the fall plowing would destroy the leaf-spot fungus that would 
otherwise live over winter in these fields on crop debris, horse- 
nettle, jimsonweed, goundcherry, and black nightshade. 
Ordinary plowing will not thoroughly cover the vines. Vines 
only partly covered are even more favorable for the developmem 
of Septoria than those lying on the surface, for the covered parts 
act somewhat as roots by keeping the exposed parts moist. The 
work of covering the vines can be facilitated by cutting them with 
a disk and plowing them under with the aid of a weedhook or 
a weedhook and jointer. The disk should not bury the vines very 
deeply, however, or they will be brought to the surface again by 
the plow. 
