THE CITRUS THEIPS. 29 



CONTROL EXPERIMENTS. 



PLAN OF SPRAYING EXPERIMENTS IN 1911. 



The principal experiments in 1911 were conducted in an orange 

 orchard about 2 miles east of Lindsay, Cal., and about the same dis- 

 tance from the nearest foothills, lying between the latter and the 

 town. A supplementary set of experiments was conducted in an 

 orchard situated on the slope of the foothills about 2 miles from 

 the first orchard, the object being to test out practically the same 

 sprays under different conditions. The trees of the latter orchard 

 were younger than those of the former, and, as is true of most foot- 

 hill groves, worse thrips infested. The insecticides used in the two 

 sets of experiments are listed below, Series I referring to the valley 

 orchard and Series II to the foothills orchard. A further experi- 

 ment, in which 2,550 Valencia and Joppa and a number of navel 

 nursery trees were sprayed, was conducted in a third orchard about 

 2 miles from the foothills. 



Series I: Valley ranch. 



Plat No. 1. Unsprayed, check. 



2. Lime-sulphur solution (36° Baurne), 1-28. 



3. Lime-sulphur solution (36° Baume), 1-56. 



4. Unsprayed, check. 



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



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



7. Unsprayed, check 



8. Lime-sulphur solution (36° Baume), 1-86, and tobacco extract 



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



9. Lime-sulphur solution (36° Baume), 1-86, and tobacco extract 



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



10. Lime-sulphur solution (36° Baume), 1-86, and tobacco extract 



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



11. Cresol soap, 1-500, and tobacco extract (40 per cent nicotine 



sulphate), 1-800. 



12. Cresol soap, 1-500, and tobacco extract (40 per cent nicotine 



sulphate), 1-1,600. 



13. Unsprayed, check. 



14. Fish-oil soap, 1-250, and tobacco extract (40 per cent nicotine 



sulphate), 1-800. 



15. Fish-oil soap, 1-250, and tobacco extract (40 per cent nicotine 



sulphate), 1-1,600. 



16. Sulphur-soda solution, 1 1-25. 



1 The sulphur-soda solution (plats 16 and 17) was prepared as follows: 



Powdered sulphur pounds 30 



Powdered caustic soda (98 per cent) do 15 



Water to make gallons 30 



The sulphur was made into a paste with water and the soda added, while the mixture 

 was constantly stirred, in sufficient quantity to cause boiling, a little water being added 

 occasionally to retard the cooking. When all the sulphur was dissolved, enough cold 

 water was added to make a stock solution of 30 gallons. A clear, amber liquid, much 

 resembling good lime-sulphur, was the result. 



