22 BULLETIN 003, II. S. DEPARTMENT OF AGRICULTURE. 



appearance to the vines. Scarcity of rapid-growing terminal shoots 

 and absence of tendrils are characteristics of stunted vines. Plate 

 I, figure 1, shows a young vineyard which is uninfested and in which 

 the vines have made normal growth. Plate II shows a small phyl- 

 loxera " spot " in an old vineyard, the photograph showing stunted 

 vines in the foreground. Plate III and Plate I, figure 2, indicate 

 badly infested old vineyards, in which all the vines are phylloxe- 

 rated and most of them badly stunted. The vine in the foreground 

 of Plate III is obviously stunted, although less so than its neighbors. 



PHYLLOXERA ROOT LESIONS. 



Root lesions are swellings on grape roots caused by the puncture 

 of the phylloxera beak. They are of two types, (1) nodosities and 

 (2) tuberosities. 



The nodosity. — Nodosities (PI. IV, fig. 1) are rapidly growing 

 swellings on the white fleshy feeding rootlets. They soon acquire 

 a characteristic greenish-yellow color, and curve and bulge around 

 the phylloxera? responsible for their inception so that the insects 

 come to lie in a depression (PI. IV, fig. 1, h). A nodosity may be- 

 come as much as six times the diameter of the normal size of the root 

 when several insects have settled upon it, and about twice the di- 

 ameter for a single occupant'. Through its size, form, and color, 

 the nodosity is very conspicuous in comparison with the root and is 

 manifest proof of the presence of the phylloxera. 



In most cases the formation of a nodosity arrests the growth of the 

 rootlet. At times the rootlet grows one-fourth inch or so in length, 

 and occasionally the puncture of the phylloxera does not affect the 

 rootlet in its growth, the subsequent swelling acquiring a lignous 

 character and becoming a tuberosity. Nodosities are generally short- 

 lived, lasting about a month. Excess moisture hastens their decay, 

 lack of moisture dries them up, but a low, even temperature causes 

 them to last longer. 



The foregoing also applies to the American variety of vines styled 

 nonresistant. On the rootlets of the resistant American vines the 

 phylloxera? frequently fail to cause swellings, and when nodosities 

 are produced they are smaller, less fleshy, and brown in color. At 

 times, though no swelling occurs, the rootlet dies at the point of 

 puncture. 



The tuberosity. — Tuberosities (PI. IV, figs. 2, 4) also are swellings 

 caused by the puncture of the aphid. Though of a similar nature, 

 they differ from nodosities in form because of the lignous character 

 of older roots. They occur on all parts of the root system of vinifera 

 vines except at the apex of the growing fibrous rootlets. They may 



