THE CITRUS THRIPS. 35 



The relative worth of the spray mixtures in this series may be 

 divided roughly into four groups, according to their relative merits, 

 as follows : 



1. Sprays raising about three-fourths of the injured fruit from third to 



first grade : 

 Lime-sulphur (33° Baume), 1-75, and tobacco extract (2| per cent 



nicotine sulphate), 1-150. 

 Lime-sulphur (33° Baume), 1-75, and tobacco extract (2| per cent 



nicotine oin iohate), 1-100. 

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



2. Sprays raising about one-half the injured fruit from third to first grade : 



Tobacco extract (2| per cent nicotine sulphate), 1-100. 



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



Cresol soap, 1-400, and tobacco extract (40 per cent nicotine sulphate), 



1-1,600. 

 Fish-oil soap, 1-200, and tobacco extract (40 per cent nicotine sulphate), 



1-1,600. 

 Fish-oil soap, 1-200, and tobacco extract (40 per cent nicotine sulphate), 



1-2,400. 



3. Sprays raising about one-third of the injured fruit from third to first 



grade : 

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

 Cresol soap, 1-400, and tobacco extract (40 per cent nicotine sulphate), 

 1-2,400. 



4. Without insecticidal value: 



Plain water at high pressure. 



As indicated by the figures in Table IX, insecticides in the first of 

 the foregoing groups raised from 31 to 33 per cent out of a probable 

 41 per cent of third-grade fruit to first grade; i. e., over three- 

 fourths of it; those in the second group, only about 20 per cent, or 

 about half of it; and those in the third group prevented only about 

 one-third of the injury. 



The results from the more effective sprays in Series II may be 

 stated in terms of the gross receipts of the fruit. The difference in 

 price per box between the grades for this particular fruit was as 

 follows : First-grade fruit brought 67 cents more per box than third- 

 grade and 29 cents more than second grade, which brought 38 cents 

 more than third-grade fruit. The differences in receipts per hundred 

 boxes between sprayed plats 1, 2, and 10 and the check plat are given 

 below : 



Plat 1. — 33.3 boxes raised from third grade to first grade, at 67 cents $22. 31 



0.2 boxes raised from second grade to first grade, at 29 cents — . 06 



Amount received per 100 boxes sprayed fruit in excess of 



the unsprayed 22. 37 



Plat 2.— 31.7 boxes raised from third grade to first grade, at 67 cents__ 21. 23 



7.6 boxes raised from second grade to first grade, at 29 cents 2. 20 



Amount received per 100 boxes sprayed fruit in excess 



of unsprayed 23. 43 



