THE CONTROL OF TOMATO LEAF-SPOT 
tions, plate cultures, and inoculations of tomato plants with aqueous 
extract from the soil, are shown in Table 2. 
Table 2. — Results from adding soil to cultures of the tomato leaf-spot fungus 
exposed during winter 
Culture medium (sterilized) 
Condition of culture 
before the addition 
of soil and its expos- 
ure to winter tem- 
perature 
Kind of soil 
added to 
culture 
Condition of culture the fol- 
lowing spring and summer 
Age 
(days) 
Growth 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
3 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
18 
Not examined. 
do 
_do 
Sterilized 
do 
...do... 
No growth. 
Mixed field grasses.. . .. 
No viable Septoria. 
Pycnidia and spores present. 1 
No pycnidia or spores. 
Do. 
Do. 
Ambrosia artemisiaefolia 
Amaranthus retroflexus 
Chenopodium alba 
do 
do 
do 
do 
do 
do 
do 4 
do 
do 
do 
do 
Fair 
do 
do 
do 
do 
Unsterilized... 
do 
do 
do 
do 
do 
do 
Sterilized 
do ... 
do 
No growth. 
C r a bgrass 
Mixed field grasses . . 
No Septoria present. 
Do. 
Do. 
Ambrosia artemisiaefolia 
Amaranthus retroflexus 
Chenopodium alba 
Do. 
Do. 
Do. 
Do. 
C rabgrass 
Mixed field grasses 
No viable S?ptoria. 
Do. 
Do. 
do 
Ambrosia artemisiaefolia 
Amaranthus retroflexus 
Chenopodium alba 
Fair 
None 
do 
Fair 
do 
do 
do 
....do 
Do. 
No growth. 
Do. 
No viable Septoria. 
do 
_do 
Unsterilized— . 
-do 
Do. 
Do. 
Abundant 
do 
Do. 
Fair 
..do . 
Do. 
Amaranthus retroflexus 
Chenopodium alba 
None 
do . 
do 
do 
No growth. 
Do. 
Fair. 
...do 
No viable Septoria. 
1 These pieces of cornstalk were rather thick and large in proportion to the quantity of soil used. No 
growth was obtained when a much larger proportion of soil was used. 
The addition of soil to the cultures destroyed the viability of 
Septoria lycopersici during the winter, except in some tubes con- 
taining cornstalks. As the pieces of cornstalk were rather thick the 
fungus may not have obtained the full effect of the soil in these tubes. 
In the presence of unsterilized soil in the 3-day set and of both 
sterilized and unsterilized soil in the 18-day set, Septoria cultured on 
cornstalks lost its viability during the winter. Similar results were 
obtained on all the other media covered with soil and exposed to the 
same temperatures. 
CONTROL MEASURES 
USE OF EARLY PLANTS 
As previously stated, the tomato leaf-spot fungus not only has a 
narrow range of sporulation temperatures, viz, 59° to 80.5° F., but 
requires a month at 59° to produce spores. Because of these tem- 
perature limitations it is greatly retarded in its development and does 
not usually appear on plants in the field in the Middle Atlantic and 
Middle Western States before the middle or latter part of June. 
Consequently the use of very early plants offers a means of escaping 
much of this disease. Moreover, an earlier crop would have more 
favorable temperature conditions for the production of fruit, as the 
average temperature during the growing season in this region is 
somewhat above the optimum. 
