New York Agricultural Experiment Station. 295 



on the hibernating habits of the insect as previously noted showed 

 plainly that situations in which dead weeds or grasses abound 

 or where leaves from trees collect provided the best conditions 

 for the wintering of the leaf-hoppers. Observations on the 

 early movements of the insects in the spring also demonstrated 

 that vineyards badly infested with this species were always 

 adjacent to locations attractive for purposes of hibernation or 

 where spring food-plants existed. The infestation of the grapes 

 extended from such places outward across the vineyard. Fig. 2 

 is a sketch of a vineyard that presented a very unfavorable condi- 

 tion during the spring and early summer. It will be noted that 

 the proximity of portions of the vineyard to grass fields, grassy 

 headlands, wooded banks of a stream, blackberries, and rasp- 

 berries determined the relative amount of leaf-hopper injury to 

 the vines, as is indicated by the shading. This vineyard had been 

 allowed to produce considerable weeds and summer grasses dur- 

 ing the previous season and for that reason the insects were found 

 throughout the area, but the portions having the greatest infesta- 

 tion were always adjoining situations that provided favorable 

 winter quarters and spring food plants. In fact most vineyards 

 whose owners have systematically " cleaned up " adjacent weedy 

 and neglected land were free from excessive injury at least until 

 August and usually the entire summer. "While it is true that 

 the nymphs and adults of the summer brood inflict much injury, 

 owing to numbers, considerable damage is done by the hibernat- 

 ing adults in the spring since they attack young foliage, causing 

 yellowing of the leaves, which is very noticeable in some years. 

 This injury takes place at a time when it is impossible to con- 

 trol the insects with sprays. This phase of the habits of the 

 hibernating adults has not been emphasized sufficiently hereto- 

 fore owing perhaps to the fact that spraying for the summer 

 brood of the nymphs has been depended on to protect the vine- 

 yard. This damage to the young grape foliage by the adults is 

 needless, however, and can largely be prevented by burning over 

 the winter quarters of the insects, which will destroy the greater 

 portion of them. 



