CITRUS SCAB : ITS CAUSE AND CONTROL. 
15 
Table 3. — Mean temperature and precipitation at Orlando, Fla.. during the months 
of January. February. March, and April m the years 1914, 1915, and 1921. 
[Temperature data are stated in degrees F., precipitation data in inches.] 
January. 
February. 
Year. 
Temperature. Precipitation. Temperature. Precipitation. 
Mean. 
Depar- 
normal. 
Depar- 
ture 
from 
normal. 
Depar- Depar- 
«-. £5 To,a..|S 
normal. normal. 
1914 
69.4 
58. : 
6-3.7 
-0. 2 5. 23 
- . 5 : 4. 36 
-3.5 .52 
4-2.83 
-1.96 
- ■ 
62.2 -1.0 3.31 
60.3 - .9 4.34 
64.1 -2.6 1.76 
-0.62 
1915 
-1.65 
1921 
- .89 
March. 
April. 
Temperature. Precipitation. Temperature. Precipitation. 
Total depar- 
ture from 
normal. 
Year. 
Mean. 
Depar- 
ture 
from 
normal. 
Total. 
1914 62 -5.6 
1915 99. 2 S.4 
1921 7 . 
2.10 
1.41 
.-7 
Depar- ; Depar- 
ture M ture 
from Mean - from 
normal. normal. 
D tu P re r " Tem " Pre - 
Total. y"* per- cipita- 
nSESl. ■*>">■ «-. 
72.9 -2.1 
- .89 68.4 -2.4 
-1.44 72.6 -1.5 
2.25 + .29 
- 2.3 
+3.54 
.10 -1.10 
-12. 2 : 
+1.62 
1.51 - .82 
+ 13.4 
-5.23 
It will be noted that the mean temperatures for all three seasons 
are reasonably well within the infection range mentioned by Fawcett, 
while the rainfall was above normal during 1914 and 1915, years of 
eitrus-seab abundance, and considerably below normal for the same 
period in 1921, when citrus scab was very slight. Figure 2 shows the 
daily range of temperature and the precipitation during these four 
months of 1915. while Figure 3 is a thermographic record 4 for a 
representative week during the scab season. Figure 4 gives the 
temperature range during the comparatively scab-free spring of 
1921. With the progress of the rainy season of the summer of 1921 
numerous complaints were registered in regard to a severe citrus- 
scab outbreak on the current crop of June bloom fruit, especially on 
trees which showed little or no spring infection but abundantly 
supplied with affected leaves from the 1920 growth. Many nurseries 
which were only slightly affected with scab during the spring of 1921 
were very severely attacked during the summer of that year. It 
thus appears that infection is possible over a wide range of tempera- 
tures, and that moisture conditions during periods when young 
flushes are putting out determine in the main the seasonal prevalence 
of citrus scab. 
Conclusions regarding the general behavior of the disease on its 
several hosts when based on the behavior of the disease on bearing 
4 The graphs shown in Figures 3 and 6, while not dependable for maximum and minimum range, 
rather accurate account of the length of time that the high and low temperatures were maintained. 
