36 BULLETIN 616, U. S. DEPARTMENT OF AGRICULTURE. 



Plat 10. — 30.9 boxes raised from third grade to first grade, at 67 cents $20. 70 



4.4 boxes raised from second grade to first grade, at 29 cents 

 per box 1.27 



Amount received per 100 boxes sprayed fruit in excess 



of unsprayed 21.97 



Taking into consideration the fact that only two early applica- 

 tions were made in Series II, at the foothills ranch, it will be seen 

 that in seasons like 1911, when the infestations are light, reasonably 

 successful commercial spraying may b.e depended upon to insure an 

 increase of at least 25 cents for every box of sprayed fruit over the 

 unsprayed fruit. 



RESULTS IN NURSERY SPRAYING EXPERIMENTS. 



That portion of the nursery designated as Plat 1 was sprayed 

 thoroughly with a gasoline-power outfit used in orchard work. The 

 trees in Plat 2 were given equally careful treatment, being well 

 drenched each time, but the spraying was done with a small, hand- 

 power outfit, fitted with a nozzle of the Vermorel type. The results 

 from the use of the gasoline-power outfit were greatly superior 

 to those from the hand-power outfit, demonstrating the greater effi- 

 ciency of the former. In October the trees sprayed with the gas- 

 engine outfit looked so remarkably clean and vigorous that they 

 attracted attention; at this time they had a good growth of about 3 

 feet, without curled leaves and with but little of the whitish dis- 

 coloration characteristic of thrips injury to leaves. On the trees 

 sprayed with the hand-power outfit the proportionate growth was 

 somewhat less and thrips marking was noticeably more severe. 



CONCLUSIONS FROM SPRAYING TESTS. 



In the foregoing two sets of tests the following insecticides and 

 combinations gave the best results. Any of these mixtures may be 

 relied upon to give satisfactory control when properly applied. 



1. Lime-sulphur solution, — If the lime-sulphur is of a density of 36° Baume, 

 dilute 1 gallon with 56 gallons of water ; if of a density of 33° Baume, dilute 

 1 gallon with 50 gallons of water. 



2. Sulphur-soda solution. — Two gallons of the stock solution, prepared as 

 described on page 29, diluted with 25 gallons of water. 



3. Lime-sulphur and tobacco extract (40 per cent nicotine sulphate). — Dilute 

 1 part of the lime-sulphur, if 34 to 36° Baume, with 86 parts of water; if 30 

 to 33° Baume, with 75 parts of water. Then add 1 part of the tobacco extract 

 to 1,000 parts of the lime-sulphur as diluted above. 



4. Tobacco extract (40 per cent nicotine sulphate). — Dilute 1 part with 800 

 parts of water. 



Lime-sulphur and soda-sulphur solutions are more effective against 

 the citrus thrips than any other mixture thus far tested, and par- 

 ticularly the lime-sulphur at the strength stated above. A large per- 



