94 MANUAL OF VEGETABLE-GARDEN INSECTS 



attacked by a later flight if a second migration occurs. Injury 

 by the leafhopper is likely to take place in regions not infested 

 the previous year and a season of severe injury may be fol- 

 lowed by one in which practically no leaf hoppers can be found. 

 In most localities the disease is of a periodic nature, but in 

 certain regions within the permanent breeding area infestation 

 is almost sure to occur every year. 



In feeding, the insect punctures the leaf with the slender 

 needle-like bristles of its beak and sucks out the juices of the 

 plant, at the same time inoculating it with the virus of the 

 disease. When disturbed, the leafhoppers spring quickly into 

 the air and take wing, but soon alight seeking shelter on another 

 ])lant. When on the wing they appear white. The female 

 inserts her eggs their full length singly in the stems, midrib 

 and petiole of the leaves and sometimes in the larger side veins. 

 The eggs are pale, elongate, slightly curved and narrower 

 anteriorly. Before hatching the growth of the leaf usually 

 forces the eggs part way out of the tissue. The eggs hatch in 

 about two weeks and the minute, nearly colorless nymphs begin 

 feeding on the leaves down in the center of the plant. The 

 older nymphs vary from creamy white in color to nearly black, 

 variously spotted and mottled with brown, buff and red. 

 In about three weeks the nymphs become mature, having 

 passed through five immature stages in the course of their 

 growth. The eggs are laid during a considerable period, from 

 late in June to the first of September in the northern part of 

 the insect's range, but the greater number are deposited during 

 the first half of July. Each female is capable of laying about 

 80 eggs. There is only one generation annually. 



The control of this leafhopper and the consequent elimina- 

 tion of the curly-leaf disease is commercially unsolved. The 

 adult hoppers are hard to hit and difficult to kill with contact 

 insecticides and it is doubtful whether spraying would be com- 

 mercially profitable. Something can be gained, however, by 



