THE CITRUS WHITE FLY: INJURY. 
23 
figures, since, according to Mr. Walker, the best prices were not paid 
for sooty-mold-blackened fruit until late in the season after the clean 
fruit had nearly all been shipped or disposed of. Clean fruit at this 
time would have been proportionally more profitable. 
INJURY TO TREES. 
Weakening of vitality. — It is doubtful if the white fly is ever the 
direct cause of the killing of trees, limbs, or twigs in well-fertilized 
groves. It does, however, seriously stunt the growth of all heavily 
infested trees, and may temporarily entirely check the growth of 
young trees. Its greatest effect on the vitality of the tree is an indi- 
rect one. Infestation by the white fly appears to weaken the resist- 
ance of orange and tangerine trees to foot rot, die back, melanose, 
wither tip, and drought, and favors the multiplication of the purple 
and long scales which are second to the citrus white fly as citrus pests 
in the Gulf coast regions. 
Depreciation in value. — The selling values of citrus groves are greatly 
reduced by white-fly infestation, and citrus nurseries have their ter- 
ritory for sales much restricted and values reduced. Concerning the 
reduction in value of groves of bearing trees one of the most experi- 
enced dealers in orange groves in the State estimates that it is in 
general about one-third. For years California has been closed to 
Florida nurserymen as a field for the sale of citrus nursery trees, and 
a similar quarantine regulation has recently gone into effect in Ari- 
zona. In Florida and in citrus-growing sections of other Gulf coast 
States a guaranty of freedom from white fly is generally required, 
especially when the purchaser contemplates planting a more or less 
isolated grove. 
SUMMARY OP LOSSES. 
The estimates in the foregoing pages refer to ordinary losses where 
the white fly is unchecked by natural enemies or by artificial methods 
of control and not to exceptional or occasional losses. These esti- 
mates, as applying to the fruit, are summarized in Table III. 
Table III. — Estimates of losses to orange crops by white fly in uncontrolled condition. 
Maximum. 
Minimum. 
Mean. 
Ripening retarded 
Per cent. 
5 
50 
10 
6 
5 
10 
Per cent. 
2 
20 
1 
2 
1 

Per cent. 
35 
Number and size of fruits 
Cost of cleaning 
Deterioration in shipping quality 
5* 
4 
Indirect injury: Increased scale and disease effects on fruit 
3 
Loss in market value 
5 
Total 
86 
26 
56 
