Puant Lice Insurina FourAce AND Fruit or toe APPLE 757 
When abundant the lice cause the leaves to curl, but not so markedly 
as does Aphis sorbi. The leaves never form a close, tight curl, as is so 
common with the latter species, but the curl is more open, the tip of the 
leaf rarely doing more than touching the base. Later in the summer, 
usually in late July and August when there is sometimes a severe out- 
break of Aphis pom, the curling of the foliage may be more marked 
(Plate X). This is particularly true as the lice congregate on the rapidly 
growing twigs, stunting them and causing all the foliage to curl badly and 
in many cases to turn black and die. In young orchards-serious damage 
may be done by the dwarfing and stunting of the rapidly growing shoots. 
As the fruit begins to set, it may be attacked by countless swarms of 
these green lice, which congregate about the calyx end, on the stalk, and 
around the base, of the apple. The action of these numerous pumps 
at work sucking out the juices of the apples causes them to become elongated, 
puckered, and distorted, with many characteristic creases on the surface 
(Plates X—XII). Such badly injured fruits may drop in great numbers 
in June, considerably reducing the expected crop; or they may remain 
on the trees and become hard and knotty, growing to a slight extent and 
usually forming clusters —the so-called “‘cluster fruits’? (Plate XII). 
The apple crop has been seriously injured in this way in many sections 
in the past few years. 
Where this plant louse is abundant it greatly reduces the vitality of the 
trees, prevents the formation of fruit buds, distorts and deforms the foliage, 
often kills many of the succulent shoots, and causes knotty and gnarled 
apples. Recent experiments have shown that it also seems to be an active 
agent in the transmission of fire blight, one of the worst diseases in nurs- 
eries and in apple and pear orchards. 
THE ROSY APPLE APHIS 
The rosy apple aphis (Aphis sorb/) hatches during the same period as 
‘the green apple aphis. It first attacks the opening buds, appearing to 
be particularly attracted to the flower buds (Plate XIII). In these the stem 
mothers congregate, and their progeny soon swarm over the developing 
leaves, the opening flowers, and the flower stalks. When the lice are 
abundant they may prevent the flowers from opening properly, and cause 
the flower stalks to weaken and oftentimes to bend to one side. The 
