May a,192 x 
Collar-Rot of Tomato 
181 
COMPARATIVE INFECTIOUSNESS OF VERTICIEEIUM EYCOPERSICI, MACRO- 
SPORIUM SOLANI, AND RHIZOCTONIA SOLANI 
Experiments were made to determine the relative infectiousness of 
these fungi and the difference in type of lesion they produce. Small 
plants were inoculated as previously described by placing mycelium or 
mycelium and spores from a fresh culture against the stem at or a little 
below the soil line. 
Table I gives the number and percentage of infections obtained within 
two to three weeks after the inoculations were made. 
Table I. —Results of inoculating tomato seedlings with collar-rot fungi when plants were 
not placed in a moist chamber 
Fungus. 
Epidermis lightly scratched be¬ 
fore inoculation. 
Epidermis not injured before 
inoculation. 
Number 
of plants 
inocu¬ 
lated. 
Number 
of plants 
ihfected. 
Percent¬ 
age of 
plants 
infected. 
Number 
of plants 
inocu¬ 
lated. 
Number 
of plants 
infected. 
Percent¬ 
age of 
plants 
infected. 
Verticillium lycopersici . 
180 
180 
IOO 
466 
37 2 
80 
Macrosporium solani . 
57 
57 
IOO 
380 
319 
84 
Rhizoctonia solani. .. 
92 
47 
51 
466 
72 
15 
Control. 
0 86 
X 
I 
0 Number of plants used but not inoculated. 
As shown by the table, Verticillium lycopersici and Macrosporium 
solani produced a high percentage of infections even when applied to an 
uninjured epidermis. Rhizoctonia solani , on the other hand, produced a 
much smaller percentage of infections, especially when the epidermis 
was not injured in the process of inoculation. 
In order to determine whether Rhizoctonia solani would have pro¬ 
duced a higher percentage of infections under more humid conditions 
another set of inoculation experiments was made in which the plants 
were kept in a moist chamber 48 hours after inoculation. The results 
are shown in Table II. 
Table II .—Results of inoculating tomato seedlings with collar-rot fungi when plants 
were kept in a moist chamber 48 hours after inoculation 
Fungus. 
Epidermis lightly scratched 
before inoculation. 
Epidermis not injured before 
inoculation. 
Number 
of plants 
inocu¬ 
lated. 
Number 
of plants 
infected. 
Percent¬ 
age of 
plants 
infected. 
Number 
of plants 
inocu¬ 
lated. 
Number 
of plants 
infected. 
Percent¬ 
age of 
plants 
infected. 
Verticillium lycopersici . 
6 
6 
IOO 
21 
27 
33 
°I 5 
19 
23 
4 
2 
90 
85 
12 
13 
Macrosporium solani . 
Rhizoctonia solani . 
18 
18 
IOO 
Control. 
° Number of plants used but not inoculated. 
36731°—21 -6 
