70 



PROTECTION OF PLANTS, 1921-22 



of the feeding period they migrate to potatoes and beans and begin mating and 

 egg laying. 



The eggs are about V30 of an inch 

 long and are transparent at first. 

 They are deposited in the petiole and 

 midribs of leaves where they change 

 from transparent white to yellow. 

 In from ten days to two weeks the 

 eggs hatch and the young nymphs 

 appear as whitish, wingless hoppers. 

 They begin to feed at once and as 

 they absorb the plant juice they 

 grow and become green. They shed 

 the skin five times during their grow- 

 ing season and become winged adults 

 in about seventeen days. When 

 quite young they are to be found 

 mostly on the lower side of the leaves 

 and they move about but little. 



The adult females have a long egg 

 laying period and nymphs in all 

 stages may be found up to the time 

 of the first frost. 



The first generation of the season 

 causes the first noticed hopperburn 



Fig. 1 The potato leafhopper.^A. Egg in ^n the potatoes. Adult females of 



leaf tissue; B. First nymphal stage; C. Second this generation give rise to a second 



stage; D. Third stage; E. Fourth stage; F. p.p,-,p,.ation durino- tbp spa son and 

 Fifth stage; G. Adult stage; H. Outer (elytron) geneiation auimg tne season ana 



and inner wing, showing venation. After Bull, usuallv the severest attack of hop- 



334. Wisconsin University Agr. Exp. Sta. pgrburn occurs at the period when 



adults of the first generation and nymphs of the second generation are 

 feeding at the same time. The over — wintering leaf hoppers are members of 

 the second generation. 



Varietal Susceptibility 



In Quebec the Irish Cobbler appears to be more susceptible to leaf hopper- 

 burn than Green IVIountain. Unfortunately the writer does not happen to have 

 at the present moment facts relative to susceptibility for other potato growing 

 areas of Canada. In Wisconsin Early Triumph is affected worst and Rural 

 New Yorker least . An important point to notice is that early planted potatoes 

 are hable to suffer more from hopperburn than late planted varieties. It is also 



