32 



BULLETIN 616, U. S. DEPARTMENT OP AGRICULTURE. 



in the different check plats shows the uncertainty of the infestation 

 and the necessity, in order to obtain reliable comparison, of several 

 interspersed lots of unsprayed trees. The comparisons would be still 

 more accurate if it had been feasible to leave single untreated trees 

 interspersed among the sprayed trees of each plat, but the work of 

 keeping the fruit from a large number of scattered trees in 17 plats 

 separate for examination would involve too much time and expense, 

 and there would be much risk of the pickers, paid by the box, mixing 

 the fruit. 



Table VII. — Comparison of fruit sprayed for the citrus tlirips with that un- 

 sprayed, Series I, Lindsay, Cal., 1911. 



No. 



of 



plat. 



Amount of fruit 

 examined. 



Treatment of trees. 



Num- 

 ber of 

 loose 

 boxes. 



Num- 

 ber of 

 oranges. 



Commercial grading of fruit. 



Number 

 of first- 

 grade 

 oranges. 



Number 

 of second- 

 grade 

 oranges. 



Per cent 

 first- 

 grade 



oranges. 



Per cent 

 second- 

 grade 

 oranges. 



Untreated 



Lime-sulphur (36° Baume), 1-28 



Lime-sulphur (36° Baume), 1-56 



Untreated 



Tobacco extract (40 per cent nicotine 

 sulphate), 1-800 



Tobacco extract (40 per cent nicotine 

 sulphate), 1-1,600 



Untreated 



Lime-sulphur (36° Baume), 1-86, and 

 tobacco extract (40 per cent nicotine 

 sulphate), 1-800 



Lime-sulphur (36° Baume), 1-86, and 

 tobacco extract (40 per cent nicotine 

 sulphate), 1-1,600 



Lime-sulphur (36° Baume), 1-86, and 

 tobacco extract (40 per cent nicotine 

 sulphate), 1-2,400 



Cresol soap, 1-500, and tobacco extract, 

 1-1,600 



Cresol soap, 1-500, and tobacco extract 

 (40 per cent nicotine sulphate), 

 1—2,400 ; 



Untreated 



Fish-oil soap, 1-250, and tobacco ex- 

 tract (40 per cent nicotine sulphate), 

 1-800 



Fish-oil soap, 1-250, and tobacco ex- 

 tract (40 per cent nicotine sulphate), 

 1-1,600 



Sulphur-soda, 1-25 



Sulphur-soda, 2-25 



Resin wash, 1-3 



Resin wash, 1-5 



Resin wash, 1-10 



Plain water 



Untreated , 



20 



2.386 

 2, 308 

 2,243 

 2,180 



2,300 



2,281 



2,442 



2,337 



2,420 



2,387 

 2,345 



2,126 



2,648 



2, 555 



2,444 

 2,563 

 2,622 

 2,700 

 2,760 

 2,596 

 2,639 

 2,650 



1,981 

 2.285 

 2, 225 

 1,734 



2,247 



2,160 



2,188 



2,272 



2,321 



2,174 

 2,071 



1,740 



1,878 



2,299 



2,041 

 2,294 

 2,510 



( 2 ) 

 ( 3 ) 



2,191 

 2,176 



405 

 23 

 18 



446 



53 



121 



254 



213 



274 



386 

 770 



256 



403 

 269 

 112 



C 1 ) 



( 2 ) 

 ( 3 ) 



448 

 474 



83.1 

 98.9 

 99.1 

 79.4 



97.5 



94.6 



89.5 



97.1 

 95.8 

 91 



81.8 

 70.8 



83.4 

 89.4 

 95.7 



0) 



( 2 ) 



( 3 ) 

 82.9 

 82 



16.8 

 1 



20.4 

 2.3 



5.1 

 10.4 



2.7 



11.6 



18.1 

 29 



16.4 

 10.4 

 4.1 



(') 

 ( 2 ) 

 ( 3 ) 



16.9 



17.8 



1 83.6 per cent of fruit injured by spray. 



2 69.6 per cent of fruit injured by spray. 



3 43.7 per cent of fruit injured by spray. 



The fruit from plats 1 and 4 was considered as one unsprayed lot 

 for comparison with the sprayed fruit from plats 2 and 3 ; that from 

 plats 4 and 7 as a check on the same from plats 5 and 6, etc., in 

 order to get unsprayed fruit as nearly as possible representative of 

 what sprayed fruit would have been without treatment. More than 



