THE ORANGE THRIPS. 
11 
and when both larvae and adults were present. The second applica- 
tion was made eight days later, and the third three weeks after the 
second, at which time the thrips began again to be numerous. All 
the spraying was done with a hand outfit, maintaining a pressure of 
140 pounds. 
In recording the results of the spray applications to ascertain their 
efficiency it was necessary to class the fruit, as regards injury, in four 
grades, as follows : 
Sound: No thrips marking. 
Slightly marked : A slight marking at one end or a few streaks on the surface. 
Moderately marked : Both ends of fruit marked and some scabbing on the rest 
of the surface. 
Badly marked: Nearly one-half to three-fourths of the surface marked, often 
\A r ith misshapen fruit. 
At picking time 20 loose, or " lug," boxes of oranges from the 
sprayed trees and 20 from an adjoining block of unsprayed trees 
were counted. The results obtained are given in Table II. 
Table II.— Injury to sprayed and unsprayed fruit by orange thrips. 
SPRAYED. 
Num- 
ber of 
loose 
boxes. 
Total 
number 
of oranges 
exam- 
ined. 
Num- 
ber 
sound. 
Number 
slightly 
marked. 
Number 
moder- 
ately 
marked. 
Number 
badly 
marked. 
Per cent 
of sound 
fruit. 
Per cent 
of slightly 
marked 
fruit. 
Per cent 
ofmoder- 
ately 
marked 
fruit. 
Per cent 
of badly 
marked 
fruit. 
20 
2,070 
1,533 
506 
31 
74.5 
24.5 
1 

UNSPRAYED. 
20 
2,365 
337 
1,047 
710 
271 
14.5 
44.5 
30 
11 
'A commercial grading of the spra}^ed fruit would have placed 
nearly 75 per cent as " Fancy " and the remainder as " Choice," while 
the unsprayed fruit would have run not more than 15 per cent 
" Fancy " and 50 per cent " Choice," the remainder going out as 
" Standards " and " Culls." Of the fruit counted from the unsprayed 
trees, 85.5 per cent was marked, while 25.5 per cent only of that from 
the sprayed trees showed injury, indicating that 60 per cent of the 
sound fruit was due to the spraying. The thrips-marked fruit was 
smaller than the sound fruit, as will be seen by comparing the total 
number of oranges from the 20 boxes of sprayed fruit with that from 
the 20 boxes of unsprayed fruit. The writers have frequently noticed 
in the packing houses that the smaller fruit is worse marked than the 
larger, making it appear that the thrips injury holds back the growth 
of the oranges. 
