74 THE GRAPE ROOT-WORM. 



observation, when the maximum number of eggs had been deposited, 

 and before but few larvse had hatched from the earhest deposited 

 eggs. 



All of the bark was carefully stripped from the vine and a count 

 made of the egg clusters found. The number of eggs in these clusters 

 may vary from 3 or 4 to 75 or even 100. Since it was impossible to 

 make an actual count of the individual eggs, the clusters were classi- 

 fied, as the count was made during the examination of the vines, as 

 large when they contained approximately 50 eggs or more, medium 

 when they contained about 30 eggs, and small when they contained 

 about 10 eggs. In this manner we obtained the estimated number of 

 eggs per vine given in the Table XXVI dealing with egg deposition. 

 A simple enumeration of the number of egg clusters deposited per 

 vine regardless of the number of eggs which they contained would 

 have given but an inadequate idea of the total number of larvae which 

 might infest the roots of these vines. The number of canes per vine 

 is also given to indicate the size of the vine, since the limit of the area 

 upon which the beetles could deposit eggs would have some influence 

 on the number of clusters deposited. 



The prevalence of larvae at the roots of vines in sprayed and 

 unsprayed plats was determined by making careful diggings at the 

 roots of a given number of vines in both the sprayed and the 

 unsprayed plats (Table XXVII). During these diggings the differ- 

 ence in the number of root fibers thrown out by vines in the sprayed 

 and unsprayed plats was very noticeable. On May 13, 1908, after 

 the vineyard had received the protection of one season's treatment 

 with poison spray the root systems of several vines were examined 

 in the block of young Concords. It was found that the roots of 

 many of the vines in the unsprayed plat were almost entirely devoid 

 of new root fibers, and that the large roots were badly channeled and 

 pitted by the feeding of the larvae of the grape root-worm, whereas 

 the roots of vines examined in the sprayed portion of this vineyard 

 showed that they had thrown out large masses of new fibrous roots 

 during the growing season as a result of the protection the spraying 

 had afforded them in the prevention of the deposition of eggs by the 

 beetles. Plate IV, figure 1, will illustrate this luxuriant growth of 

 new root fibers on roots of sprayed treated vines, practically all of 

 which were produced during the growing season of 1907, as compared 

 with the lack of them on the unsprayed vines (PL IV, fig. 2). These 

 illustrations also indicate the recuperative power of badly injured 

 grape vines when protection from the larvae is afforded; for in the 

 spring of 1907, previous to the protection of the vines by the poison 

 spray, the roots of the vines in the sprayed plat were as devoid of 

 root fibers as were those in the unsprayed plat, as was shown by dig- 

 gings made in the spring of 1907. , 



