THE CITRUS THRIPS. 



33 



95 per cent of the grade reduction occurring in the orchard was 

 caused by thrips injury. The efficacy of the various insecticides in 

 raising the grade of the fruit is shown in Table VIII. 



Table VIII. — Efficacy of the spray mixtures in Series I. 



Unsprayed fruit. 







Sprayed fruit. 



















Grade-rais- 





Number of 



Number of 





Number of 



Number of 



ing efficacy 

 of the 



Plat No. 



boxes first- 



boxes low- 



Plat No. 



boxes first- 



boxes low- 



sprays. 





grade fruit. 



grade fruit. 





grade fruit. 



grade fruit. 

















Per cent. 



1 and 4. 



81 



19 



2 



99 



1 



95 









3 



99 



1 



95 



4 and 7. 



85 



15 



5 



98 



2 



87 









6 



95 



5 



67 



7and 13. 



80 



20 



8 



97 



3 



85 









9 



96 



4 



80 









10 



91 



9 



55 









11 



88 



12 



40 









12 



82 



18 



10 



13 and 22. 



79 



21 



14 



90 



10 



52 









15 



84 



16 



24 









16 



90 



10 



52 









17 



96 



4 



81 









21 



83 



17 



19 



The relative worth of the spray mixtures in Series I, as indicated 

 in Tables VII and VIII, may be summarized as follows : 



1. From 80 to 90 per cent grade-reducing injury prevented by — 



Liine-sulphur (36° Baume), 1-28. 



Lime-sulphur (36° Baumg), 1-56. 



Tobacco extract (nicotine sulphate 40 per cent), 1-800. 



Lime-sulphur (36° Baume), 1-86, and tobacco extract (40 per cent 



nicotine sulphate), 1-800 and 1-1,600. 

 Sulphur-soda solution, 2-25. 



2. Between 60 and 80 per cent of injury prevented by — 



Tobacco extract (40 per cent nicotine sulphate), 1-1,600. 



3. From 50 to 60 per cent of injury prevented by — 



Lime-sulphur (36° Baume), 1-86, and tobacco extract (40 per cent 



nicotine sulphate), 1-2,400. 

 Fish-oil soap, 1-250, and tobacco extract (40 per cent nicotine sulphate), 



1-800. 

 Sulphur-soda solution, 1-25. 



4. Less than 50 per cent of injury prevented by — 



Cresol soap, 1-500, and tobacco extract (40 per cent nicotine sulphate), 



1-1,600. 



' Fish-oil soap, 1-500, and tobacco extract (40 per cent nicotine sulphate), 

 1-2,400. 



Fish oil soap, 1-250, and tobacco extract (40 per cent nicotine sulphate), 



1-1,600. 

 Plain water. 



5. Fruit and leaves severely injured by — 



Resin wash, 1-3 ; 1-5 ; and 1-10.' 



Contrary to expectation, the addition of soaps to tobacco solutions 

 did not appear to increase their efficacy, but, on the contrary, seemed to 

 lower it. Straight tobacco extract with 40 per cent nicotine sulphate, 



