THE HOMOPTERA 



201 



directly favor the successful migration of this pest, and as far as possible 

 therefore, no elms should be allowed to grow near apple orchards. 



For the root form, when sufficiently injurious to make it pay, removing 

 the earth to a depth of six or eight inches over the root area and pouring 

 kerosene emulsion or nicotine sulfate diluted as above, over this exposed 

 surface, using enough to thoroughly wet the ground, has given good 

 results. 



Nursery stock affected can be dipped in the lime-sulfur wash or 

 in these materials, when dug either for transplanting or sale, and as 

 the Northern Spy seems to be rather free from this pest, using trees 

 grown on stocks of that variety is desirable. 



The Grape Phylloxera (Phylloxera vitifolicE Fitch). — This aphid is a native 

 of America and attacks the grape. Native American vines, however, are resis- 

 tant to its work to a considerable degree, so that injury to them is not serious. 



Fig. 193. — Under surface of Grape leaf showing galls produced by the Grape Phylloxera 

 {Phylloxera vih/olice Fitch). Somewhat reduced from natural size. (From Riley, U. S. 

 D. A.) 



The European grape (Vitis vinifera) on the other hand, is very susceptible to 

 its attacks and when the Phylloxera reached Europe about 1860, it became very 

 destructive, causing the loss of over two million acres of vineyards before any 

 successful checks to the insect were discovered. In this country it reached 

 California where the European grape is also grown, about 1874 and has been the 

 cause of great injury there also. 



The insect lays its eggs, one per female, on old wood of the grape in the fall, 

 and these eggs hatch the following spring into tiny Uce which locate on the upper 

 surface of the young leaves and begin to suck the sap. This causes the leaf to 

 become depressed at each place where a louse is at work, so that galls (Fig. 193) 

 projecting from the under surface are soon produced, m which the insects live. 

 Upon becoming full-grown these Uce lay eggs in the galls and the young which 

 hatch from them pass to other parts of the leaves and produce galls of their 



