SPRAYING AGAINST THE GRAPE LEAFHOPPER. 7 



foliage only with considerable difficulty. It is in this stage, as men- 

 tioned in a previous paragraph, that the insect becomes disseminated 

 over vineyard areas. Nevertheless, the spread of the adults does 

 not become general until late in the season, when migration for the 

 purpose of hibernation takes place. This feature of its movement 

 was adequately and strikingly demonstrated in several vineyards 

 where experimental work was carried on against the nymphs during 

 the season of 1910. In no case was there a serious reinfestation of 

 the thoroughly treated vines, although adjoining untreated rows 

 were heavily infested throughout the entire season. Hence, we are 

 led to the belief that widespread dissemination of this pest takes 

 place largely during the fall migration, when the adults rise in the 

 air and are carried by the winds, and, again, during the spring mi- 

 gration, when they leave their winter shelter and return to the vines. 

 Thus the vineyardist who has been successful in destroying the 

 nymphs during the summer need have little apprehension of rein- 

 festation later in the season from adjacent infested and untreated 



vineyards. 



REMEDIAL MEASURES. 



In discussing the subject of remedial measures for the control of 

 an insect pest, it is always highly desirable to take into considera- 

 tion cultural and other operations involved in the production of the 

 particular crop under treatment in order that the recommendation 

 of methods of control which may conflict with the most desirable 

 farm practice, or may be impracticable on a commercial scale, may be 

 avoided. Modifications in vineyard or orchard management by the 

 adoption of new methods may also seriously conflict with earlier 

 recommendations which were quite feasible when first suggested. 

 Thus, earlier writers have laid considerable stress upon the value of 

 clean culture of vineyards and the gathering up of all trash and 

 leaves in and bordering upon them as a means of greatly reducing 

 the number of overwintering " hoppers." Unfortunately, however, 

 this cleaning-up process is impracticable over large areas, and it 

 not infrequently happens that adjacent rough lands which furnish 

 winter protection outside the vineyards are not under the control 

 of the owner of the vineyard. Furthermore, the practice of grow- 

 ing winter cover crops of clover, vetch, turnips, etc., in vineyards, 

 a practice highly desirable both from the standpoint of increasing 

 the fertility of the soil and preventing soil wash during the winter 

 months, has become quite general throughout Erie County (see PL 

 I, figs. 1 and 2). There is no doubt that cover crops tend to hold 

 more of the hoppers in the vineyards than where clean culture is 

 practiced. Yet many vineyardists are convinced that the ultimate 

 advantage to the vine is so much in favor of the cover crop that they 

 prefer to continue this practice, if possible, and look for some other 



