APHIDS 51 
(Black Leaf “40” 1 to 800 or Black Leaf 
1 to 50). A badly infested. tree will re- 
quire three gallons or more. The lice 
hibernating on the trunk can be destroyed 
by a winter application of lime-sulphur. 
The stock of the Northern Spy Apple is 
resistant to the Woolly Aphis. 
PEAR. See Apple. 
QUINCE. See Apple. 
POMEGRANATE. See Apple. 
PLUM AND PRUNE 
The Mealy Plum Aphis 
Hyalopterus arundinis Fabr. 
This is a longish, rather narrow aphid. 
It is pale green in color and is covered 
with a whitish mealy powder. It inhab- 
its the plum during winter and spring, 
_ often becoming intensely abundant on 
the leaves during March and April. In 
May the great majority of the lice be- 
come winged and migrate to grasses, but 
a few remain on the plum during the 
Fig. 8. 
Twigs. 
Galls Caused by Woolly 
Aphis on 
—Hssig 
ee 
Fig. 9. Effect of Woolly Aphis on Root. 
—Hssig. 
summer. Migrants return in October to 
the fruit trees and produce the sexed 
forms. The winter eggs are laid on the 
twigs around the axils of the buds. This 
aphid is a cosmopolitan species and is 
probably of European origin, and it and 
the two following plum plant-lice may 
be controlled in the manner advised for 
the Green Apple Aphis. 
The Hop Aphis 
Phorodon humuli Schrank 
This is a pale green non-pulverulent 
aphid at times injurious to plums. Its 
life history is similar to the preceding 
species, the alternate host-plant being the 
hop. 
The Rusty-brown Plum Aphis 
Aphis setariae Thos. 
This is a small rusty-brown aphid 
which often infests the young leaves and 
