442 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



the spray be applied with much force in order that it may 

 penetrate the woolly secretion that covers the insects. The 

 root forms are harder to control, as it is difficult to reach them. 

 But if the earth is removed from all of the roots that are within 

 eight or ten inches of the surface, and those affected then 

 treated with kerosene emulsion or tobacco extract, most of 

 the aphids may be destroyed. If the ground is thoroughly 

 wet with the emulsion or tobacco it seems to act as a repellant 

 and the roots may not be infested again for some time. As it 

 is the young trees that suffer most from the attacks of this 

 insect, great care should be taken to see that the pest is 

 not introduced into the orchard with nursery stock. No 

 nursery stock that shows any indication of having been at- 

 tacked by this aphis should be accepted, for by no treatment 

 can it be made absolutely safe. Nursery men often sprinkle 

 tobacco dust on the ground along the rows of growing young 

 trees. This not only kills some of the aphids that are close 

 to the surface, but it acts as a repellant, for a while at least. 

 Trees grown on Northern Spy stock do not seem to be as 

 seriously attacked as those grown on other roots. 



Black Peach Aphis (Aphis persica-niger.} There are 

 several other species of aphids that attack the peach, plum and 

 other orchard trees, usually confining their attacks to the 

 foliage or tender twigs. The black peach aphis is of particular 

 importance because, like the woolly aphis of the apple, it attacks 

 the roots as well as the leaves and branches. Both the winged 

 and the wingless aphids may be found on the foliage during 

 the summer, but winged forms do not seem to occur on the 

 roots. The aphids may be found on any of the roots through- 

 out the year, but they do most damage to the smaller roots. 

 As they cling tenaciously to the roots they are very apt to be 

 distributed on nursery stock, and great care should be taken to 

 keep them from being introduced into the orchard in this way. 

 The colonies are established on the foilage in the spring by some 

 of the larvae migrating from the roots. The methods suggested 

 for controlling the woolly aphis should be used in fighting this 

 species. 



