34 
BULLETIN 616, U. S. DEPARTMENT OF AGRICULTURE. 
diluted 1-800 and 1-1,600, respectively, gave better results than at the 
same strengths with the addition of soaps. This fact is difficult to 
account for, but may be due partly to more severe infestation of the 
trees on which the soap was used than on those sprayed with the 
unmodified tobacco extracts. The soap plats were located two on 
either side of check plat 13, in which there was 29 per cent of low- 
grade fruit; but the comparison is made with the average between 
plats 13 and 22, in which there was 21 per cent low-grade fruit. The 
infestation may have been as severe in the soap plats as in check 
plat 13. The plats treated with straight tobacco extracts lay be- 
tween check plats 4 and 7, with only 20 and 5 per cent low-grade 
fruit, respectively. The foregoing explanation does not hold, how- 
ever, for the similar results from soap and tobacco extracts, under 
different conditions, in Series II, and the latter experiments seem to 
lend further weight to the probability that but little benefit will re- 
sult from adding soaps to tobacco extracts as sprays for the citrus 
thrips. Experiments under very heavy and uniform thrips infesta- 
tion, however, might result somewhat differently. 
RESULTS IX SERIES II. 
The fruit from the experimental plats in Series II was packed in 
three commercial grades instead of two, as was that of Series I. The 
results from spraying are given in percentage of fruit of each of the 
three grades, from all the separate plats, in Table IX. 
Table IX. — Comparison of fruit sprayed for tlie citrus thrips with that ini- 
sprayed, Series II, Lindsay, Cal., 1911. 
Plat 
No. 
Treatment of trees. 
Lime-sulphur (33° Baume), 1-75, and 
tobacco extract (2f per cent nicotine 
sulphate), 1-150 
Lime-sulphur (33° Baume), 1-75, and 
tobacco extract (2§ per cent nicotine 
sulphate) , 1-100 
Tobacco extract (2| per cent nicotine 
sulphate), 1-100 
Tobacco extract (40 per cent nicotine 
sulphate), 1-1,600 
Tobacco extract (40 per cent nicotine 
sulphate), 1-2,400 
Cresol soap, 1-400, and tobacco extract 
(40 per cent nicotine sulphate), 1-1,600 
Cresol soap, 1-400, and tobacco extract, 
1-2,400 
Plain water 
Untreated 
Tobacco extract (40 per cent nicotine 
sulphate), 1-800 
Fish-oil soap, 1-200, and tobacco extract, 
(40 per cent nicotine sulphate), 1-1,600. 
Fish-oil soap, 1-200, and tobacco extract, 
(40 per cent nicotine sulphate), 1-2,400. 
Amount of fruit 
examined. 
Num- 
ber of 
boxes. 
Number 
of 
oranges. 
2,492 
2,504 
2,371 
2,502 
2,711 
2,336 
2,403 
2,582 
2,271 
2,176 
2,147 
2,049 
Commercial grading of fruit. 
Per cent 
first- 
grade fruit. 
40.3 
46 
25.7 
33 
19.2 
30.2 
22.2 
7.4 
6.7 
42 
30 
27.4 
Per cent 
second- 
grade fruit. 
51.8 
44.4 
53.1 
46.6 
54 
48.3 
52.8 
46.7 
52 
47.6 
51.3 
50.7 
Per cent 
third- 
grade fruit. 
7.8 
9.4 
21 
20.2 
26.7 
21.3 
24.7 
45.7 
41.1 
10.2 
IS. 6 
21.8 
