176 INTERNATIONAL CONGRESS OF VITICULTURE 



methods has been practically the only one followed in California, and since 

 this is a viticultural, rather than an entomological problem, it will not be 

 further discussed. 



GRAPE LEAF-HOPPER. 

 Typhlocyba comes, Say. 



The grape leaf-hopper occurs in numbers sufficient to be a pest in the 

 Sacramento, San Joaquin and Imperial valleys. It rarely becomes injurious 

 in the Coast valleys or the grape sections of Southern California aside from 

 the Imperial and Coachella valleys. The injury occasioned by the grape 

 leaf-hopper is indicated by the leaf becoming at first a silvery color, later 

 turning to yellow and finally to brown, when it drops from the vine. Leaves 

 thus affected occur most commonly about the crown of the vine, though in 

 cases of serious injury all of the leaves will show this effect. Many of the 

 leaves may become functionless or drop off as early as June or July, and 

 this early loss of foliage prevents the berry from maturing properly. The 

 lack of full foliage to the end of the season also prevents the canes from 

 ripening normally for next year's wood. The buds fail to develop in the 

 following spring, and thus the vine may be more or less permanently stunted 

 in growth in serious cases or hopper injury. 



The grape leaf-hopper passes the winter as an adult insect which may 

 feed on various plants growing in the vineyard or the vicinity during the 

 warmer weather. During cold or wet weather the hopper remains under 

 leaves or rubbish or low down on the plants upon which it feeds. When the 

 vine comes into leaf in the spring the hopper leaves its winter food plants 

 and feeds exclusively on the grape leaf until the leaves fall in the autumn. 



The young hoppers, or nymphs, begin to hatch about the first of May in 

 the Fresno section, a little later farther north, and two or three weeks 

 earlier in the Imperial Valley, in the extreme south. The young of the 

 second generation begin to appear in the latter part of June, making two 

 generations of the insect in a season. 



Probably the most generally satisfactory method of control for the grape 

 leaf-hopper is spraying for the nymphs or young. The adults are almost 

 impossible to kill with the spray, while the nymphs are very susceptible to 

 several different kinds of spray material. The chief difficulty in spraying is 

 to get the material on the under side of the vine where the hoppers are, and 

 there is a further objection that the eggs which are within the tissues of the 

 leaf, as well as the adults, which are also present, are not affected by the 

 spray. In spite of these drawbacks, spraying for the nymphs will pay when 

 the hoppers are abundant and doing much damage. The spray found most 

 efficient in killing the young, as well as most neutral to the grape foliage 

 and berry, is as follows: 



Blackleaf, 40 per cent 1 pint 



Liquid soap (or hard soap 2 Ibs.) % gallon 



Water 200 gallons 



One of the most important factors in hopper spraying is the time of 

 application. If the spray is applied too early, too many eggs which have not 

 yet hatched will escape because the spray cannot reach them; if too late, 

 many young will have become adult winged hoppers which cannot be killed 



