INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 



65 



body becomes dark red. The young. are white or light yellow with very 

 faint red spots. The eggs are very small, semi-transparent, bean-shaped 

 and about 1-34 inch long. 



Life History. — According to Professor H. J. Quayle, the eggs are 

 inserted just beneath the epidermis on the underside of the grape leaves 

 and hatch in from fifteen to twenty days. The young nymphs begin 

 at once to feed upon the first appearing foliage, by extracting the juices 

 from the leaves with the sharp beaks. There are two broods a year: 

 winter and summer. The adults of the former hibernate and begin 

 feeding upon the first foliage in the spring. 

 During May they begin egg-laying, which 

 gives rise to the summer brood. This brood 

 grows very rapidly and lays eggs within a few 

 weeks, dying off in the fall. Their eggs give 

 rise to the coming winter brood. Thus the 

 destruction may begin in May and end only 

 when all of the leaves have fallen. 



Nature of Work.— The young and adult 

 hoppers feed upon the undersides of the 

 leaves, causing them to turn yellow or brown 

 and to fall prematurely. In cases of severe 

 infestation so many of the leaves may fall as 

 to prevent the ripening of the crop. 



Distribution.— This hopper occurs through- 

 out all of the vine-growing sections of the 

 State, and is especially abundant in the San 

 Joaquin and Sacramento valleys. 



Food Plants. — The principal and prac- 

 tically the only host during the summer 

 months is the foliage of various kinds of 

 grapes, but during the winter such low-grow- 

 ing succulent plants as alfalfa, clover, filaree, grasses, mustard and 

 ragweed are attacked, while in the spring the foliage of beech, black- 

 berry, burdock, catnip, currant, dewberry, gooseberry, grasses, maple, 

 raspberry, strawberry and Virginia creeper become food plants. 



Control.— Spraying should be done when the hoppers are in the 

 nymphal stage, about the last of May or the first of June. A spray con- 

 taining .02 of one per cent nicotine or a nicotine-soap spray ("black 

 leaf 40," 1 pint, soap 4 pounds, water 200 gallons) gives good results 

 if applied under from 150 to 200 pounds pressure as a coarse driving 

 spray. Screen cages, large enough to cover a vine, with a bottom to fit 

 around the trunk, one open side and smeared on the inside with crude 

 oil, may be placed over the vine with the open side facing the wind. 

 Upon jarring the vines through the slit the excited hoppers, in trying 

 to escape, are caught in the oil on the sides and bottom. In this way 

 large numbers are caught. To be of any value this method must be 

 used in the spring, before egg-laying begins. Specially constructed 

 suction devices for drawing in the hoppers by air currents have also 

 been tried in the San Joaquin Valley, but without financial success. 



Clean culture to eliminate all food plants in the vineyard and around 

 the edges should not be neglected in the fight to control this pest. 



Fig. 54. — The grape leaf- 

 hopper. Erythroneura comes 

 (Say). Adult female, sum- 

 mer form. Natural size 

 shown by line at the right. 

 (After Johnson) 



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