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AJV ECONOMIC ENTOMOLOGY. 



tested in the Atlantic States to make it possible to either encour- 

 age or discourage its use. It has the advantage of being very 

 thorough where it is at all effective, but the outfit required for 

 large trees is expensive. 



Sulphur is an insecticide of comparatively limited range, but it 

 seems in some cases to prevent injury and has almost a specific 

 effect upon many of the mites which become troublesome in hot- 

 houses. It is sometimes applied by dusting the flour of sulphur 

 directly upon the plants, but is more usually applied in a watery 

 mixture. Many nurserymen place a considerable quantity of 

 crushed or powdered sulphur in a barrel and fill it with water, 

 stirring at intervals, and allowing it to remain for days or even 

 weeks, using from it and adding water as necessary. By boiling 

 with lime, the sulphur can be entirely dissolved, and a more 

 effective mixture will be obtained. In orange groves sulphur is 

 largely used against the rust mite, and is effective by simply 

 spreading it over the surface of the ground. It seems to cause a 

 slow fumigation of the trees sufficient to destroy the mites. Cu- 

 riously enough, this remedy seems less satisfactory on the 

 Pacific coast than it has been found in the East. 



Gas-tar is sometimes recommended for certain purposes as an 

 insecticide, and more frequently as a repellent ; but it is rarely 

 of any practical value. It never serves to repel from any sur- 

 face which it does not cover and mechanically protect, — that is to 

 say, its odor will not prevent insects from attacking plants near 

 it. It has been suggested that by placing it around the base of 

 plants like squashes, the borers can be prevented from entering 

 the plant ; but the moths will simply lay their eggs a little way 

 from it, and the caterpillars, when hatched, bore into the stem at 

 any point not actually touched by the tar itself Another 

 method that has been recommended is to put a quantity of tar 

 into a barrel and fill up with water ; then stir occasionally until 

 the water becomes impregnated with whatever it can dissolve 

 out. This, it has been said, is useful against plant-lice ; but I 

 have never found any beneficial effects from it, and deem it of 

 altogether too uncertain a value to be recommended. 



Naphthaline has been used as an insecticide, but is of compara- 

 tively little value in the field, where its cost will prevent its gen- 

 eral use. The vapor given off by it is offensive and even poi- 



