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 IN SEEIES 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 the citrus thrips with that un- 

 sprayed, Series II, Lindsay, Col., 1011. 



Plat 

 No. 



Treatment of trees. 



Amount of fruit 

 examined. 



Num- 

 ber of 

 boxes. 



Number 



of 

 oranges. 



Commercial grading of fruit. 



Per cent 



first- 



grade fruit. 



Per cent 

 second- 

 grade fruit. 



Per cent 

 third- 

 grade fruit. 



Lime-sulphur (33° Baum6), 1-75, and 



tobacco extract (2| per cent nicotine 



sulphate), 1-150 



Lime-sulphur (33° Baum6), 1-75, and 



tobacco extract (2J per cent nicotine 



sulphate), 1-100 



Tobacco extract (2f 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, l-200 ; and tobacco extract, 



(40 per cent nicotine sulphate), 1-2,400. 



2,492 



2,504 



2,371 



2,502 



2,711 



2,336 



2,403 

 2,582 

 2,271 



2,176 



2,147 

 2,049 



40.3 



46 



25.7 



33 



19.2 



30.2 



22.2 

 7.4 

 6.7 



42 



30 



27.4 



51.8 



44.4 



53.1 



46.6 



54 



48.3 



52.8 

 46.7 

 52 



47.6 



51.3 



50.7 



7.8 



9.4 



21 



20.2 



26.7 



21.3 



24.7 

 45. 1 

 41.1 



10.2 



18.6 



21.8 



