368 Report of the Department of Ka'tomof^xtY of the 



quarters. As soon as they have fed again upon grape foliage in 

 the spring these areas become yellow. 



Experiments have proven that a spray containing 2/100 of one 

 per ct. nicotine is the most effective and safest contact insecti- 

 cide for the control of the grape leaf-hopper. This must be di- 

 rected against the nj^mphs, which are hit by applying the spray 

 to the under sides of the leaves. 



The application of the spray for this insect can be done by the 

 usual hand spraying with trailing hose or by an automatic leaf- 

 hopper sprayer which is described in this bulletin. This latter 

 device was developed during the past season and it has done 

 efficient work. With high pressure and proper adjustment of 

 the nozzles the insect can be efficiently controlled. 



INTRODUCTION. 



Tlio grape leaf-liopper (I'yphiocyha comes Say) (Fig. G), or, 

 as it is often called, " grape tlirips," is a very common insect in 

 the vineyards of New York State. Although its numbers during 

 years of average infestation are not sufficient to cause apprehension 

 on the part of the growers as a whole, nevertheless each year some 

 grape plantings are injured by its feeding. Its work is especially 

 noticeable in vineyards near woodland or grass-land, which affords 

 good hibernating places for the insects. The grape leaf-hopper, 

 like other insects, has periods of scarcity and abundance, and when 

 abundant it is very destructive, compelling the growers to resort to 

 remedial measures. 



During the summer of 1910 it was seen that this insect was 

 becoming very numerous in Chautauqua county, the browned 

 foliage and poorly ripened fruit, resulting from its work, showing 

 plainly in many vineyards. Observations in 1911 soon proved the 

 number of "hopper-infested " vineyards greater than in 1910; in 

 fact, the increase of the insect was so great as to cause alarm on 

 the part of the grape growers, since a large crop of fruit had set 

 which was threatened both in quality and quantity. The attack 

 affected chiefly the quality, although several vineyards sliowed a 

 marked decrease in the yield between the vines upon which the 



