JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol.'14 



to ascertain the nmnber of nymphs and adults present in the field. 

 These results were plotted as shown in Figure 2. It is seen that there 



Fig. 2. Chart showing relation of leafhopper population to per cent, of tip- 

 burn, a, number of nymphs; b, number of adults; c, per cent, of tipburn. 



Fig. 3. Chart showing relation of climatic factors to per cent, of tipburn. c, per 

 cent of tipburn; d, degrees minimum humidity; e, degrees maximum temper- 

 ature; /, number hours sunshine. 



