14 THE GRAPE ROOT-WORM. 



the roots. In the breeding work, however, larvae were reared on 

 wild grapevines, which shows that it is possible for the larvae to 

 exist on these plants. In 1909 larvae hatching July 26 were placed 

 in large earthen pots (fig. 22) in which, some time previously, wild 

 grapevines had been planted. On examining the cages in the fall 

 of the same year (1909) a number of larvae were found to have 

 attained their normal growth, as compared with other larvae reared 

 under similar conditions on cultivated vines. 



CHARACTER OF INJURY AND DESTRTJCTIVENESS. 



The injury wrought by this pest on the grapevine occurs both 

 above and below the surface of the ground ; however, by far the greater 

 damage results from its work upon the roots. The injury above the 

 ground is done by the beetles; that upon the roots by the grubs or 

 larvae. 



The first intimation that the observant vineyardist is likely to 

 obtain of the presence of this pest upon his vines is the appearance, 

 late in June or early in July, of chainlike markings upon the upper 

 surface of the foliage (PI. II). These markings are made by the 

 beetle. Ordinarily this scoring of the leaves is not sufficient to 

 materially affect the health of full-grown thrifty vines. Where the 

 beetles are very numerous, however, and the foliage sparse, it not 

 infrequently happens that the leaves are so badly scored that in a 

 short time they take on a brown appearance and hang about in 

 shreds. In the case of newly planted vines (fig. 29) extensive 

 feeding by the beetles greatly retards the growth of the young plant 

 and proves a great obstacle in the starting of a new vineyard. On 

 the thick-leaved varieties of grapes, such as the Concord, Worden, 

 and Niagara, this feeding does not extend through the heavy pubes- 

 cence on the lower surface. The pubescence holds together only a 

 short time, however, and soon either dries out or is torn apart by 

 the growth of the leaf. On the thin-leaved varieties, as the Dela- 

 ware, and on the wild species of grape, holes are eaten entirely 

 through the leaf, usually assuming the characteristic chainlike irregu- 

 larity of form. 



It is, however, to the larvae of this pest feeding upon the roots of 

 the vines that the direct cause of the injury and death of so many 

 vines is due. The work of the larvae upon the roots may be recog- 

 nized, when the vines are removed from the soil, by the absence of 

 root fibers, by channels along the larger roots, and by pittings on 

 the main trunk. (See PL III.) Vines that have become well 

 established before the infestation by larvae will sometimes withstand 

 the attack of a considerable number of grubs, especially if the soil 

 is rich and has been well tilled. The evidence of continued heavy 

 infestation is indicated by absence of fibers upon the whiplike roots 



