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 brassice 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 
lice 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- 
Fig. 252.— Work of the Cabbage Aphis. Original. mer. 
Spray thoroughly 
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. 
The Potato Plant-louse (\Wacrosiphum 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 
