624 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



are necessary. Horton 1. c., summarizes the spraying recommenda- 

 tions based on spraying tests made in California as follows: 



"In the 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 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, 



FIG. 535. Graphic illustration of the seasonal activities of the citrus thrips 

 as related to blossoming and later growth periods of the orange and 

 indicating also the spray periods. After Horton, U. S. Dept. of Agr. 



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 particularly the lime-sulphur at the strength stated above- 



* The sulphur-soda solution was prepared as follows: 



Powdered sulphur 30 pounds 



Powdered caustic soda (98 per cent) 15 pounds 



Water to make 30 gallons 



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. 



