citrus -cab: rrs cause axd gotstbol.. 
19 
Table 1. — Mea md precipitation at Orlando. Fla., during the months of 
. . Jvne. July, an'] August in the years 1018. 1919, and l < 
Temperature data are 
stated 
in degrees F ., 
precipitation data in inches.] 
! 
May. June. 
Temperature. Precipitation. Temperature. 
Precipitation. 
Extn 
De- 
par- 
ture 
from 
nor- 
mal. 
De- 
par- 
Extremes. 
Mean. 
De- 
par- 
ture? 
from 
nor- 
mal. 
Total. 
De- 
par- 
Maxi- 
mum. 
Mean. 
Mini- 
mum. 
ture 
from 
nor- 
mal. 
Maxi- 
mum. 
Mini- 
mum. 
ture 
from 
nor- 
mal. 
1918 
1919 
1920 84.3 
63.1 7.\ 5 -1.4 
63.2 7*5.2 -.7 
:..-. +1.6 
2.11 
10.37 
6.72 
-1.7 
-6. 56 90. 5 
1 " 1 91.2 
67.8 
31 
+0.6 
-1.0 
-.9 
5.37 
5.19 
5.89 
-1.89 
-2.07 
-1.27 
Year. 
July. 
August. 
For 4 months. 
Temperature. 
Precipita- 
tion. 
Temperature. 
Mean. 
De- D* 
par- par- 
}™± TotaL L m * 
Extremes. 
Maxi- Mini- 
mum, mum. 
1919. . 
193).... 92.7 
from 
nor- 
mal. 
from 
I nor- 
mal. 
Mean. 
Maxi- Mini- 
mum, mum. 
69.4 
70.3 
70. 1 
80.1 -0.2 
8L4 -.7 11.49-4 
7"..-. 
81. i 
De- 
par- 
Precipits 
tion. 
De- 
par- 
ture ™^._, ture 
from 
nor- 
mal. 
Total. 
from 
nor- 
mal. 
3.34 
5.49 
-3.81 
-1.69 
Departure 
from nor- 
mal. 
Pre- 
Tem- • • 
™*- Uo'n. 
-0.9 -1.9 
-2.1+6.04 
-.5 +5.37 
Mean 
tem- 
pera- 
ture. 
79.7 
79.8 
78.77 
It will be noted that in spite of the fact that the mean tempera- 
ture is in general well above the limit- set by Fawcett, the mean 
minimum temperatures for summer arc usually well within that 
range, but it is probable the temperature does not remain in that 
lower zone sufficiently long for infection to progress at a rapid rate. 
If it is assumed that the pathogen is present in quantity, there 
are three other factors which play their part< in completing infec- 
tion, viz, (1) suitable temperature limits. (2) abundant moisture, 
and (3) host parts in a stage of development susceptible to infection. 
The relative scarcity of citrus scab in both orchards and nurseries 
situated in the drier sections of Florida and in the drier seasons, 
together with the fact that citrus scab has not been able to estab- 
lish itself in California lemon orchards with their drier climatic 
conditions, is strong evidence that this fungus is largely dependent 
upon certain weather conditions to cause infection, namely, abun- 
dant moisture during the period when leaves are expanding and 
fruit i> setting. Such weather seldom occurs in the relatively dry 
citrus region- of California at times when the plant is >tible 
to infection: hence, the absence of scab and it- resulting financial 
