INSECTS INJURIOUS TO ORCHARD TREES 439 



tain aphids for the sake of their honey-dew. But the ants do 

 not always assume such a definite relation to the welfare of 

 the aphids. Usually they appear on aphis-infested trees only 

 to feed on the honey-dew, and neither injure nor care for the 

 aphids. The black sooty fungus that grows on this honey-dew 

 often completely covers the leaves and fruit making them very 

 dirty and disagreeable to the sight and touch. 



The Green Apple Aphis (Aphis pomi.} This is one of the 

 most common aphids found on apple trees. It feeds on the 

 tender tips of the green shoots and upon the young leaves, 

 causing the leaves to become twisted and curled in such a 

 way that they afford excellent protection for the aphids that 

 are feeding within. At any time during the summer winged 

 females may appear and fly to other trees. Early in the fall 

 the sexual generation appears and the females lay their eggs 

 on the apple twigs. During the winter time these small, shin- 

 ing black, oval eggs may be found on the twigs, usually near the 

 tips. The best method of control is to prune off and destroy 

 all of the twigs on which the eggs are found. A strong sulphur- 

 lime spray will kill many of the eggs, but it does not always 

 give entire satisfaction. As the leaves begin to curl soon after 

 the aphids attack them it is hard to reach them with any spray. 

 A good strong tobacco spray, however, will kill many of them 

 if it is used very early. Kerosene emulsion may also be used. 

 It is necessary to use considerable force with any spray for 

 these insects in order to drive it into the curled leaves. 



The Rosy Apple Aphis (Aphis sorbi}. This species resembles 

 the preceding in habits and general appearance, but the body 

 is usually rosy in color. The color may vary, however, from 

 grayish to purplish or black. The winter eggs are not as 

 conspicuous as the eggs of the green aphis, and are not easily 

 detected. It is necessary therefore to rely upon the efficiency 

 of the sulphur-lime wash for destroying the winter eggs, or 

 upon some of the contact sprays for killing the insects after 

 they have attacked the leaves. It is thought that one genera- 

 tion of these aphids leaves the apple and migrates to some un- 

 known food plant on which they may pass the principal part 

 of the summer. In the fall some of the winged females return 



