DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 



Fig. 2.— The grape leaf- 

 hopper: Nymph of 

 the first stage . Great- 

 ly enlarged. 

 (Author's illustra- 

 tion.) 



wings (figs. 2-3) that it is most readily controlled by a contact spray, 

 it was necessary to make the application several days earlier than in 

 the preceding season. In addition to this, the number of days when 

 the maximum number of nymphs was present upon the vines before 

 the earliest to hatch had developed wings was materially lessened, 

 thus shortening the period during which the greatest 

 efficiency from the spray applications could be se- 

 cured. In 1910 the maximum numbers of nymphs 

 of the first brood were present on the underside of 

 the grape leaves about July 15 and spray applica- 

 tions were commenced at that date and were con- 

 tinued until July 26 before many of the nymphs 

 had changed to adults having fully developed wings. 

 In 1911, however, the maximum numbers of 

 nymphs were present on the leaves by July 5. By 

 July 11 fully 15 per cent of the first nymphs to 

 hatch were changed to the winged form. Thus there was about a 

 week longer time during which the greatest efficiency from the 

 spray application could be secured in the season of 1910 than in 

 1911. Effective work can be done, however, after many of the 

 nymphs have developed wings, and if the wingless nymphs are still 

 quite numerous upon the leaves the work may be continued with 

 good results. Owing to the more rapid development of the immature 

 stages of the insect in 1911 than in 1910, 

 there was a partial second brood of consid- 

 erable proportions in 1911, which greatly 

 augmented the injury toward the ripening 

 season. Nevertheless, where vines were 

 thoroughly sprayed against the nymphs of 

 the first brood during the first two weeks in 

 July, only slight injury resulted from the 

 later development of nymphs on these 

 sprayed vines. 



FIELD EXPERIMENTS WITH TOBACCO EX- 

 TRACTS. 



Fig. 3.— The grape leafhopper: 

 Fully developed nymph of the 

 fifth stage. Greatly enlarged. 

 (Author's illustration.) 



During the summer of 1911 several field 

 experiments, in each case covering several 

 acres, were conducted in vineyards in the 

 township of North East, Pa. In all cases the applications were 

 made against the nymphs about the time the maximum number of 

 the first brood was present on the underside of the grape leaves and 

 before many of the oldest nymphs had changed to the winged form. 

 One thorough application at this time proved sufficient to reduce the 



