BULLETIN 198. 



THE GRAPE LEAF-HOPPER. 



179 



attacking the vine, and each year in some parts of the State it 

 occurs in very great numbers, and, in such sections, it levies a heavy 

 tax upon the vineyard interests. To give expression to this loss in 

 money value, for example, in one vineyard of about a thousand 

 acres near Madera, the owner estimated that the damage done last 

 year by hoppers would aggregate about $10,000. 



The grape leaf-hopper belongs to the class of injurious insects 

 that obtain their food by sucking the juices from the plant. Scale 

 insects and plant lice are other well known pests belonging to this 

 same general group, which obtain their food in much the same way 

 that the mosquito sucks our blood. The sharp pointed beak or 

 proboscis of the hopper (Fig. 4) is thrust into the tissues of the 

 grape leaf and the 

 liquid parts extract- 

 ed therefrom. The 

 feeding is done 

 mostly on the un- 

 derside of the leaf, 

 and those leaves 

 around the base of 

 the vine are the 

 ones first attacked. 



The first indica- 

 tion of their work 

 is a mottled appear- 

 ance of the leaf due 

 to the pale spots 

 formed wherever the 

 beak has been in- 

 serted and the green parts taken out (Fig. 1) . As the feeding continues 

 these spots become more numerous, and this pale yellow color 

 spreads over the entire surface; and finally the leaf turns brown 

 and drops off (Fig. 2). This injury has been observed as early 

 as April or May, and thus the vine from the very beginning 

 of the season is prevented from making its normal growth. As 

 the hoppers increase in numbers the injury increases with the 

 advancement of the season. In midsummer quite a large area 

 about the crown of the vine will show all the leaves pale colored or 

 completely dried up, and, in severe cases, the entire vine is thus 

 affected. This drying up and dropping off of the leaves allows the 

 sun to have free access to the fruit and may cause sunburn. We have 

 seen the fruit thus exposed and badly sunburned as early as the 

 middle of June. The falling off of the leaves prematurely also pre- 



Fig. 3. The foliage and fruit of the grape is often badly 

 smutted by the excrement of hoppers. The black 

 specks on the above leaf indicate this. 



