CITRUS SCAB: ITS CAUSE AXI) CONTROL. 
11 
an abundance of scrapings from citrus-scab lesions not previously 
disinfected were placed in sterile Petri dishes, covered with glycerin 
agar or potato-dextrose agar, and held at room temperature for 10 
or 15 days before making final records. Table 2 gives the result of 
these isolation tests made for the most part in the laboratory at 
Orlando, Fla. 
Table 2. — Results of isolation tests of citrus-scab fungus from citrus fruit and I 
Tests of Leaves. 
Date of isolation. 
Host. 
Growth developed. 
Remarks. 
Dec. 11, 1916 
. . Grapefruit 
Spring, 1916 
Verv manv colonies. 
Do 
. Round orange 
do 
Many colonies. 
Feb 14 1917 
.. Grapefruit 
.. King orange 
uma orange 
r orange 
October, 1916 
\ erv manv colonies. 
"Do. " 
Feb 15 1917 
Spring, 1916 
July 27 j 1917 
Feb. 10, 191^ 
Spring, 1917 
Do. 
do 
Manv colonies. 
Do. 
Do 
.. Rough lemon 
.. Grapefruit 
. ..do 
Do 
do 
Do. 
Feb. 20 1919 
. . Sour orange 
. . Rough lemon 
Spring, 191s 
Verv manv colonies. 
Do 
do 
Do. 
Do 
. . Grapefruit 
.. Tangelo 
('alamonrlin 
....do 
Do. 
Feb 10 1920 
Summer, 1919 
Do. 
Do 
do 
Do. 
Do 
. . Sweet bittersweet 
do 
Do. 
Oct. 24, 1920 
do 
Spring, 1920 
Many colonies. 
Nov. 5, 1920 
.. Sour orange 
do 
Nov. 19, 1920 
do 
do 
Do. 
Feb. 6 1921 
. . Grapefruit 
do 
do 
Do. 
Mar. 8, 1921 
do 
Do. 
May 9, 1921 
do 
do 
Do. 
Tests 
of Fruit. 
Date of isolation. 
Host (grapefruit). 
Fruit set . 
Remarks. 
Feb. 15, 1917 
December, 1916 
March, 1920 
Very manv colonies. 
Mav27, 1920 
. . Green, 1 finches diam- 
Do. 
June 10, 1920 
. . Green, 2 inches diam- 
eter. 
do 
No colonies. 
June 23, 1920 
. . 24 inches diameter 
do 
Do. 
Do 
.. ..do 
do 
Do. 
Julv20, 1920 
. . 3| inches diameter 
do 
Do. 
Oct. 24, 1920 
. . Half colored 
do 
Do. 
Nov. 5. 1920 
do 
do 
Do. 
Nov. 19, 1920 
.. Three-fourths colored. - 
do 
Do. 
Feb. 6, 1921 
.. Mature 
Spring, 1920 
Do. 
Mar. 8, 1921 
do 
.. ...do 
Do. 
Mar. 9, 1921 
....do 
do... 
December, 1917 
Do. 
July 23, 1918 
Do. 
Feb. 10,1920 
do 
December, 1919 
Do. 
These tests show that when once the scab fungus enters a leaf, it 
can persist there throughout the winter. This finding is corroborated 
by a large number of field observations in which new flushes devel- 
oping in close proximity to hold-over lesions were seriously affected 
by scab while more distant flushes were scab free. 
The isolation experiments further show that the causal organism 
does not persist for any great length of time in fruit. It seems rea- 
sonable to conclude from cultural data and field observations that 
the disease is seldom if ever carried over winter on fruit set in the 
spring or summer. 
