PLANT-LICE INJURING THE FOLIAGE 321 
The remedy for those below ground is to draw away the carth from 
around the base of the tree, in a circle 4 or 5 feet in diameter, and 
apply 2 to 4 pounds of tobacco dust. The lice on the foliage are best 
treated with a spray of tobacco extract, or 7 per cent kerosene emulsion. 
Plant Lice on Plum Foliage 
Three species of plant lice are more or less common on the leaves and 
tender shoots of plums, especially in the spring. They tend to collect 
in clusters, the leaves are more or less distorted and curled by their 
attack, and the flowers and fruit may be badly injured. After two or 
three generations they leave the plum and fly to other hosts. 
The Brown Plum Aphis (Aphis setarie Thos.) spends the summer 
on various grasses. It is dark in color and has white-marked legs and 
antennee. 
The Mealy Plum Aphis (Hyalopterus arundinis Fab.) is covered 
with a bluish white powder. The back of the body bears three darker 
obscure stripes, and the shape of the body is rather elongated. The 
honey tubes are short and rather thick. In summer the lice are found 
on grasses. 
The Hop Aphis (Phorodon humuli Schr.) flies to hop-vines in 
early summer, and is a pest rather on the latter than on the plum. 
The treatment is a thorough spraying with tobacco extract or 7 per 
cent kerosene emulsion just as soon as the lice are first observed. It 
is important to apply the spray promptly, before the leaves are badly 
curled. 
The Clover Mite (Bryobia pratensis Garm.) 
This tiny, 8-legged mite swarms over the foliage of clover in some 
seasons. In the West it feeds also on the leaves of various fruit 
trees, sucking their juices. The leaves attacked lose their green color 
and grow yellow and sickly. The mites survive the winter for the 
most part in the egg stage on the bark of fruit trees. See page 208. 
In summer trees should be sprayed with sulphur, 10 pounds to 50 
gallons of water, adding soap so that the sulphur will not float on top 
of the water, and keeping the mixture well stirred. Spraying with 
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