224 NEBRASKA STATE HORTICULTURAL SOCIETY 



similar habits, structures and remedies. These should be known and 

 understood by the farmer and fruit grower who have to contend with 

 them. Nearly all of these lice are rather easily destroyed when proper 

 remedies are intelligently applied to them. 



General Structure and Habits 



All of the plant lice get their food by inserting a beak and sucking 

 the sap of the plant. They never eat away the tissue of the leaf. 



Throughout the entire summer, from spring to about the first of 

 September, all of our plant lice that infest orchard trees, increase in 

 numbers by giving birth to living young. If eggs are laid at all they are 

 deposited by the last brood of females in the fall. From the fact that 

 a single louse is usually able to give birth to from seventy-five to 150 

 young, and as they mature in about eight to ten days after being born, 

 it will readily be seen that the plant lice are capable of increasing with 

 wonderful rapidity. This accounts for the fact that the lice may nearly 

 all be killed from a tree and that tree be very seriously infested with 

 the lice again within a few weeks. Usually the last brood in the fall 

 are about one-half males and one-half females. These females de- 

 posit the eggs that live over winter and the lice all die. We have an 

 exception of this rule, however, in case of the wooloy apple aphis, which 

 lives over winter as young or partly grown lice upon the trunk of 

 branches, and in all stages of growth upon the roots of the trees. 



Plant louse eggs usually hatch in the spring a little before the 

 leaf buds begin to open on the trees that they infest. These early lice 

 hatching from the eggs are always wingless in the species mentioned in 

 this bulletin, and are called stem-mothers. These stem-mothers mature 

 in a short time, are all females, and begin giving birth to young lice 

 which consitute the second brood. It is seldom that the second brood of 

 lice have more than a very few winged ones. The remainder of the 

 life history of these lice will be given under the different species treat- 

 ed. 



Apple Plant Lice — Wooly Apple Aphis 



It is a bark feeder, and it attacks both the roots, the trunk and 

 the limbs of the trees, but does not feed upon the fruit or foliage. This 

 louse is readily recognized on account of its being covered with a white 

 woolly secretion which has suggested its common name. Upon the trunk 

 and branches the lice attack either the tender bark about the scars or the 

 bark of tender new shoots. Below ground, the lice attack the bark of 

 the smaller roots, causing warty swelling upon them. If very abundant, 

 the roots are often completely covered with these smooth wart-like 

 growths which sometimes cause the roots to die and rot off. When very 

 abundant upon the very rapidly growing twigs, these lice often produce 

 abrupt swellings due to the thickening of the inner bark. Sometimes 

 these swollen portions of the limbs crack open lengthwise and the 



