New York Agricultukal Experiment Station. 369 



leaf-hoppers were killed by spraying mixtures and those not so 

 treated. It is apparent that the numbers of the insect have been 

 approaching the crest of a wave, and one cannot, at present, tell 

 whether the summer of 1911 records the "high-water mark" or 

 whether we are to expect a further increase during 1912. The 

 millions of adults that went into hibernation the past fall would 

 indicate that a favorable winter for the insects will spell trouble 

 for many of the vineyardists, since these adult " hoppers " will 

 feed on the young foliage, and, if numerous, will cause much 

 injury at a time when the grape foliage is tender and the insects 

 are most difficult to kill. 



Noting the increase in numbers of the insects in certain vine- 

 yards, experiments were conducted in 1910^ and 1911 to learn 

 better methods of control. Having found an effective remedy, 

 so far as the insecticide is concerned, during the previous year, 

 it early became evident that a better method of applying the 

 material was needed ; so more attention was paid the past summer 

 to developing a machine for applying the material than to efforts 

 in finding cheaper spra^dng materials. This bulletin has to do 

 largely with the results of experiments and the description of the 

 machine devised for applying the spray. 



THE INSECT AND ITS WOKK. 



HABITS. 



The grape leaf-hopper belongs to the group of insects that obtain 

 their food by sucking the juices of plants. They are seldom found 

 on the upper surfaces of the leaves but they usually seek the 

 under sides and there do practically all their feeding. While 

 immature the insects, then called nymphs, pass through five 

 stages or instars (Figs. 7 and 8). During the nymphal instars the 

 wings increase from mere swellings in the first instar to large wing 

 pads in the last stage. The adults have two pairs of wings or, more 

 correctly speaking, the front pair of so-called wings are wing 



1 Bulletin 331, N. Y. Agr. Exp. Sta., pp. 568-579. 



