24 WHITE FLIES INJURIOUS TO CITRUS IN FLORIDA. 
The mean of the total percentage of estimated loss is considered by 
the authors to represent about the normal loss which the citrus white 
fly is capable of causing in orange groves. It is estimated that the 
condition is reduced to about 45 per cent loss in the average infested 
grove as a result of net profits from spraying with contact insecticides 
and of the natural efficiency of fungous diseases. 
From extensive records obtained in the course of their investiga- 
tions the writers estimate that the citrus white fly infests at present 
45 per cent of the citrus groves in Florida. Of this, 5 per cent is a 
sufficient allowance to represent the groves so recently infested that 
normal abundance of the pest has not been reached. An injury of 
45 per cent in 40 per cent of the groves is equal to about 18 per cent 
of the entire value of the crop as it presumably would have been if 
the white fly were not present. 
The latest Florida citrus crop concerning which statistics are avail- 
able is that of 1907-8.!. The orange crop for that season is valued 
at $3,835,000. With an estimated total loss of about 15 per cent 
this represents 85 per cent of the value of the crop if not affected by 
the white fly. Accordingly, the estimated loss in Florida is calcu- 
lated to have been about $680,000 for oranges and similarly on the 
basis of 10 per cent loss to grapefruit on a valuation of $469,700, the 
percentage of infested groves the same as in the case of the orange 
groves, a loss of $16,700 is estimated, making the total loss in valua- 
tion of fruit about $696,700 for the crop of 1907-8. The crop of 
1908-9 was doubtless affected to the extent of $750,000 by the citrus 
white fly. 
At present the spread of the fly into uninfested groves is undoubt- 
edly faster than at the rate of 5 per cent new infestations per year. 
Even on this basis, however, the annual increase in depreciation in the 
value of Florida citrus groves due to white-fly infestation is more than 
$200,000 per year.? In addition, the citrus nursery business in Florida 
is affected to an extent hard to estimate, but which would be only 
nominally represented by $50,000 per year. 
Figures are not available which would allow approximate estimates 
to be made of the damage by the citrus white fly in the Gulf coast 
citrus-growing sections outside of Florida, but the widespread occur- 
rence of the white fly in those States indicates that the losses are 
heavy. 
INCREASED COST OF MAINTENANCE, 
The items of expense of maintenance principally affected by the 
white fly are fertilization, spraying, and fumigation. In Florida 

‘Tenth Biennial Report of the Commissioner of Agriculture of the State of Florida. 
* This is not shown by actual depreciation, for the number of groves coming into 
bearing for the first time each year more than covers the loss. 
