THE PEAR THRIPS AND ITS CONTROL. 65 



An effort should be made to kill all adults in an orchard before 

 March 15, when practically all thrips are out of the ground and when 

 oviposition begins. 



The black-leaf tobacco extract may be purchased from local agents. 

 The distillate oil emulsion can also be purchased from local dealers 

 in spraying supplies, but is prepared after the following formula: 



Hot water gallons. . 12 



Whale-oil or fish-oil soap pounds. . 30 



Distillate oil (28° Baume) gallons.. 20 



The soap is first dissolved in a kettle of boiling water and then 

 removed to the spray tank, where the oil is added. This should be 

 agitated violently and sprayed out under pressure of from 125 to 150 

 pounds into other barrels. This stock solution contains about 55 

 per cent of oil, and should be diluted at the rate of about 2 gallons of 

 the emulsion to 48 gallons of water for a 2 per cent oil solution. 



The secret of making a thoroughly good stock emulsion lies in 

 having the soap and water boiling hot, in adding the oil to this solu- 

 tion, and under no circumstances in adding the soap and water to 

 the oil, in thorough and violent agitation, and, finally, in passing it 

 through the spray nozzles under high pressure. It has been found 

 by repeated experiments that high pressure is the most important 

 factor, and an emulsion passed once through the pumps and nozzles 

 under pressure of from 150 to 160 pounds can not be improved by 

 repeating this operation. 



Fish-oil soap may be made as follows: 



Water gallons. . 6 



Lye pounds. . 2 



Fish oil gallons. . 1| 



Place the water in a caldron, add the lye, and then the fish oil, 

 and boil slowly for about two hours. This will make about 40 pounds 

 of soap or about a 5-gallon mixture. 



FERTILIZERS. 



The numerous fertilizers and soil fumigants tested have proved 

 ineffectual in killing thrips in the ground, even when applied in pro- 

 portions far beyond what could be used in ordinary practice. It is 

 evident, however, that most orchards need fertilizers to strengthen 

 the buds and to insure a more regular setting of fruit. It has been 

 demonstrated repeatedly with other crops that soil soon deteriorates 

 unless there is a rotation of crops or unless fertilizers are added. 



IRRIGATION. 



Irrigating for thrips during any time of the year is entirely ineffec- 

 tual. Their bodies are so strongly resistant to water that while in 

 the ground it is not practicable to submerge them long enough to 



