KATYDIDS INJURIOUS TO ORANGES IN CALIFORNIA. 
23 
fruit at this time was principally due to katydids and thrips. No 
fruits had fallen at this time from sprayed trees, as examination 
of the ground under 15 trees disclosed. 
At picking time it became evident that a much larger saving of 
fruit than that just indicated resulted from spraying. During Octo- 
ber and November all the fruit of all sprayed plats and checks was 
counted, from which it was found that from 60 to 100 per cent more 
fruit was produced in each of the sprayed plats than in their unsprayed 
checks. (See PI. V, fig. 1.) The trees of the different plats varied 
greatly in size and condition, however, and it was therefore necessary 
to know how many trees in each plat produced the fruit of that plat. 
By eliminating the stunted, rebudded, and dead trees, resets, and 
blank spaces in each plat it was found that the full-bearing, un- 
sprayed trees matured only 54.2 per cent, or just a little over half 
as many oranges per tree as the full-bearing trees of the spra} x ed 
plats. The saving of crop in all sprayed plats taken together due 
solely to spraying was, therefore, practically 100 per cent. A greater 
saving was effected in plats sprayed with lime-sulphur and arsenicals 
mixed than in those sprayed with arsenicals alone, the former pro- 
ducing a little over twice as much and the latter only one and one- 
half times as much fruit per tree as the checks. 
PREVENTION OF INJURY TO MATURED FRUIT. 
The results of the spraying experiments in preventing katydid 
injury to the final crop of fruit were determined by examination, in 
the field at picking time, of all oranges in all plats. For convenience 
of reference these results are shown in Table III. 
Table III. — Results of spraying experiments with lime-sulphur and arsenicals in pre- 
venting injury to oranges by katydids, Lindsay, Cal., 1912, 
Sprayed fruit. 
Unsprayed fruit. 
Insecticides and dilution. 
Percentage 
of sound 
fruit. 
Percentage 
of culled 
fruit. 
Percentage 
of sound 
fruit. 
Percentage 
of culled 
fruit. 
Plat 1: Arsenite of zinc, 2 pounds; lime-sulphur, 2 gal- 
100.00 
99.99 
99.85 
99. 85 
99.86 
99.77 
99.92 
99.92 
99.84 
Plat 2: Arsenite of zinc, 3 pounds; lime-sulphur, 2 gal- 
lons, per 100 gallons water 
Plat 3: Arsenite of zinc, 4 pounds; lime-sulphur, 2 gal- 
lons, per 100 gallons water 
0.01 
.14 
.14 
.13 
.22 
.07 
.07 
.15 
80.5 
19.4 
Plat 4: Arsenate of lead, 4 pounds; lime-sulphur, 2 gal- 
80.9 
19.0 
Plat 5: Arsenate of lead, 6 pounds; lime-sulphur, 2 gal- 
lons, per 100 gallons water 
Plat 6: Arsenate of lead, 8 pounds; lime-sulphur, 2 gal- 
lons, per 100 gallons water 
82.3 
17.6 
Plat 7: Arsenite of zinc, 2 pounds, per 100 gallons water. 
Plat 8: Arsenite of zinc, 3 pounds, per 100 gallons water. 
Plat 9: Arsenate of lead, 4 pounds, per 100 gallons water. 
Average 
99.88 
.11 
81.45 
18.55 
