Timely Hints for Farmers. 



265 



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For large trees, two to five pounds of the dust may be used. Mr. 

 Marlatt says : "The tobacco dust kills the aphides by leaching 

 through the soil, and acts as a bar for a year or so to reinfestation. 



The dust is a waste product of 

 tobacco factories and costs 

 about 1 cent per pound, and 

 possesses the' additional value 

 of being worth fully its cost as 

 a fertilizer." 



3. Bisulphide of carbon 

 can be applied in two or three 

 holes about the tree to a 

 depth of six inches to a foot, 

 and not closer than a foot and 

 a half to the tree. An ounce 

 of the bisulphide should be 

 put in each hole, and the hole 

 immediately closed. This does 

 not prevent later reinfestation, 

 and is thus inferior to the to- 

 bacco dust. 



Another woolly louse is 

 that of the elm, named Schiz- 

 oneura americcma by Riley. 

 I have found this at Mesilla, 

 New Mexico, and it is not un- 

 likely to occur in Arizona 

 wherever elms have been 

 planted. 



The naked plant-lice 

 (mostly of the genera Aphis and Siphonophora) are 

 very numerous in kinds, and infest very many different plants. 

 They are noted for their rapid increase, which ap- 

 proaches the miraculous. Professor Huxley calculated that the 

 produce of a single aphis would, in the course often generations, 

 supposing all the individuals to survive, weigh more than the 

 whole population of China. Of course the individuals never do 

 all survive ; on the contrary, most of them perish, and for this we 



FfG. 5. Woolly louse of the apple. — o 

 Root of young tree showing deforma- 

 tion produced by the lice; fo, piece 

 of root with lice upon it;o, female louse. 

 a and 6, natural size; c, enlarged (Mar- 

 latt, Circular 20, 2nd Series, Div. En- 

 tomology, U. S. Dept. Agriculture. 



