citrus scab: its cause and control. 
23 
citrus trees growing on the laboratory grounds at Orlando, Fla., 
and in a near-by bearing grapefruit grove. In addition, a limited 
number of tests were made in bearing groves at other pohn 
The inoculum used in these experiments was from pure cultures 
of the scab fungus isolated from the several highly susceptible citrus 
species, from the resistant sweet orange, and from the avocado, as 
well as from cultures received from Porto Rico. More complete data 
relative to the source of cultures are given in Table 5. 
Table 5. — Sources of cultures of the citrus-scab fungus used in inoculation tests. 
Host 
Part. 
Isolated by— 
Date. 
From— 
Leaf 
do 
(?) 
Leaf 
J. A. Stevenson... 
H.E.Stevens 
(?) 
Fruit-disease in- 
vestigations. 
do 
1917 
Porto Rico. 
Rough lemon 
Rough lemon (?) 
1916 
Florida Experiment 
(?) 
1916 
Station. 
H.S. Fawcett. 
Orlando, Fla. 
Do. 
Old fallen leaf. 
do 
Jan. o, 1917 
Feb. 15, 1917 
do 
Do. 
Do... 
do 
Do. 
Do 
do 
Dried fallen 
leaves. 
Fruit 
do 
Do. 
Do 
.do .. 
do 
Do. 
Do 
...do 
May 20, 1917 
March, 1919 
December, 1918... 
April, 1919 
December, 1916.... 
January, 1917 
July, 1916 
Do. 
Do 
.do.... 
...do... 
Winter Park, Fla. 
Sour orange 
Do 
Leaf 
....do 
Orlando, Fla. 
Fruit 
do 
Do. 
Sweet orange (Ruby 
Blood). 
Sweet orange (Pineap- 
ple). 
Satsuma orange 
Leaf 
do 
Tavares, Fla. 
do 
do 
Orlando, Fla. 
Fruit 
....do 
Thomasville, Ga. 
Leaf 
....do 
Februarv, 1917.... 
April, 1917 
March, 1919 
March, 1920 
November, 1919... 
do 
April, 1918 
Winter Garden, Fla. 
do 
do 
Do. 
Taneelo 
....do 
do 
Orlando, Fla. 
....do 
do 
Do. 
Sweet bittersweet 
....do 
do 
Do. 
.do... 
...do... 
Do. 
do 
do 
Homestead, Fla. 
In general the cultures were grown on potato-dextrose agar for 
about three weeks before being used as inoculum. A liberal quan- 
tity of the vegetative fungus was placed on wet absorbent cotton 
wads (PL XV, Fig. 2) . These plasters were so placed that the fungus 
was in contact with the part to be infected, and they were then 
covered with several layers of paraffin paper (PI. XVI), except that 
in special cases the plasters were left in contact with the parts to 
be infected for at least 24 hours. Frequently in cool weather the 
plasters were on 48 hours. At the expiration of this time the paper 
and moist cotton plasters were removed, and the inoculated parts 
left unprotected. During the progress of the work, control tests 
were made by similar methods, except that the inoculum was not 
used. 
Lesions resulting from artificial infections (PI. I, Fig. 3) developed 
in from 5 to 10 days after the inoculation was made, but in every 
case final observations were deferred 15 days or more after the 
plasters were removed. 
