56 



THE REPORT OF THE 



No. 36 



Number of Broods 



There are two broods of the grape leaf hopper, but under our conditions 

 the second brood is only a partial one. This season apparently only the first 

 brood adults which matured during July gave rise to a second brood. In the 

 insectary 7 colonies of leaf hoppers which reached the adult stage during the 

 period July 15th to July 27th reproduced; on the other hand, 11 colonies which 

 matured from July 26th to August 17th failed to lay any eggs and went into 

 hibernation. 



Nature of Injury 



The leaf hopper both as a nymph and an adult feeds almost exclusively 

 on the underside of the leaves, preferably close to the veins. The feeding results 

 in the appearance of minute white points on the upper surface of the leaf, no 

 doubt due to the destruction of the chlorophyl. These points coalesce and form 

 white spots, which, as feeding progresses, become more numerous and form 



Grape foliage injured by leaf hoppers. 



pallid areas, until the whole leaf is mottled and pallid. On badly affected 

 leaves brown dead areas form as a result of the death of the tissues, and in due 

 course these areas may spread until the whole leaf is brown and dry. Severely 

 injured foliage falls prematurely. 



Early Injury. This year mottling caused by the feeding activities of the 

 overwintering adults was quite noticeable on the inner and lower leaves by the 

 end of May, and later on in many instances dead brown areas appeared on these 

 leaves. This injury, although confined to the older leaves, made many vines 

 look very unthrifty and was sufficiently conspicuous to alarm many growers. 



Summer Injury. During July the feeding of myriads of nymphs and adults 

 in unsprayed graperies gradually deprived the leaves of their green colour, and 

 the vines became conspicuously pallid. The following month the foliage com- 

 menced to turn brown and to become dry and curled. Badly damaged leaves 

 dropped prematurely, and as a result of this many vines were largely denuded 

 of their foliage at the time the grapes were ripening. 



