202 



PESTS OF GARDEN AND FIELD CROPS 



On beans they may be killed by spraying with tobacco extract, or 

 with 5 per cent kerosene emulsion. 



The Cabbage Aphis {Aphis hrassicce Linn.) 



Cabbage, cauliflower, and related plants are subject to infestation by 

 a soft -bodied plant louse, which collects in masses on the surface of 



the leaves. The 

 Hce are green, but 

 are covered with a 

 whitish, powdery 

 secretion. 



Winter is passed 

 as eggs on old cab- 

 bage stumps or 

 heads in the field. 

 There may be a 

 dozen or more gen- 

 erations in a sum- 

 mer. 

 Spray thorouglily 

 with tobacco extract to which soap has been added, or with 5 per 

 cent kerosene emulsion, or with soap solution, 1 pound in 3 gallons 

 of water. Dip infested seedlings in the same solution before 

 setting out. Dispose of crop remnants. Judicious rotation will 

 help in delaying attack. Wild mustard and shepherds-purse should 

 not be allowed to grow near cabbage. 



Fig. 252. — Work of the Cabbage Aphis. Original. 



The Potato Plant-louse (Macrosiphum solanifolii Ashm.) 



In occasional seasons potato vines are seriously checked in the latter 

 part of summer by myriads of green, soft-bodied plant lice, which suck 

 the juices of leaf and stem. Spraying the fields with contact insecti- 

 cides, either tobacco extract or 5 per cent kerosene emulsion, will kill the 

 lice. Since the pest survives the winter on alternate host plants, es- 

 pecially shepherds-purse, clean culture and burning over waste places 



