October 



SCIENTIFIC AGRICULTURE 



57 



Other Hosts. 



Field observations .show that this insect 

 may live temi)oranly on many hosts among 

 which ai'e : bean, apple, beet, rhubarb, rasp- 

 berry, red clover, Swiss chard, strawberry, 

 cucumber, lettuce, dahlia, hcllyhock, elm. 

 box-elder, burdock, rose, etc. 



On some of the above the leaf-hopper 

 merely feeds, but on beet, apple, beans and 

 box-elder it Avill also reproduce. 



Life History. 



The potato leafhopi)er {E. Mali) lives 

 over winter in the adult stage in protected 

 places such as among thickly growing 

 weeds, in brush, etc. In June they come 

 out from their resting place and feed for 

 ten days or so on the apple and other trees 

 and shrubs, and at this time females pre- 

 dominate. At the end of the feeding per- 

 iod they migrate to potatoes and beans 

 and begin mating and e^s laving. 



PLATE 2.— The potao leafhopper. 

 A. Egg in leaf tissue; B. First nymphal stage; 

 C. Second stage; D. Third stage; E. Fourth 

 stage; F. Fifth stage; G. Adult stage; H. Outer 

 (elytron) and inner wing, showing venation. 

 After Bull. 334, Wisconsin University Agr. 

 Exp. Sta. 



The eggs are about 1/3U of an incii long 

 and are transparent at first. They are 

 deposited in the petiole and midribs of 

 leaves where they change from trans- 

 parent white to yellow. In from ten days 

 to two weeks the eggs hatch and the young 

 nymphs appear as whitish, wingless hop- 

 pers. 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 growing season and be- 

 come winged adults in about seventeen 

 days. When quite young they are to be 

 found mostly on the lower side, of tbe leaves 

 and they move about but little. 



The adult females have a long egg lay- 

 ing period and nymphs in aU stages may 

 be found up to the time of the first frost. 



The fir.st generation of the season cau- 

 ses the first noticed hopperburn on the 

 potatoes. Adult females of this genera- 

 tion give rise to a second generation dur- 

 ing the season and usually the severest at- 

 tack of hopperburn occurs at the period 

 when adults of the first generation and 

 nymphs of the second generation are feed- 

 ing 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 leafhopper-burn than 

 Green Mountain. 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 liable to suffer more 

 from hopperburn than late planted var- 

 ieties. It is also significant that plants 

 from seed of diseased vines always suffer 

 more severely tlian plants from seed of 

 healthy vines. - 



Control. 



Spraying with Bordeaux 4-4-5U is ef- 

 fective in controlling hopperburn provided 

 that the underside of the leaves is spray- 

 ed thoroughly. This is obvious when con- 

 sidering the fact that nymphs feed on the 

 underside of leaves as above noted. 



