78 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. U 



alone and with nicotine at the rate of one part of this to 800 of Bordeaux 

 mixture. Each plant was sprayed thoroughly with a small atomizer 

 spray pump, both the upper and lower surfaces of the leaves being given 

 a thorough coating. Plants were selected having two or more branches, 

 one branch being protected from the spray at the time of application 

 by being enclosed in a glass cylinder. After the spray material had 

 thoroughly dried an equal number of fertile females were introduced 

 into each cage. After ten days the females were removed and the hatch- 

 ing nymphs counted daily. It had been previously demonstrated that 

 the very young nymph remained near the point of emergence from the 

 leaf tissue for at least twenty-four hours after hatching. B}^ counting 

 the nimiber of n^Tuphs found on sprayed and unsprayed leaves it could 

 be determined whether or not the egg had been laid in tissue coated 

 with Bordeaux. The following table summarizes the results. 



'Nicotine added. 



From the above preliminary test it was found that out of a total of 

 231 fertile eggs laid by the females but 11 were deposited in sprayed 

 leaves. It was also noticed that in every case of a n\Tnph hatching 

 on a sprayed leaf, the latter was always imperfectly covered by the 

 insecticide. While there are not enough dat? to indicate the comparative 

 effect of different Bordeaux formulae on the adults, it is evident that 

 this mixture or even lime water will repel the adults under certain 

 conditions. Thus oviposition is prevented, provided the leaves are 

 thoroughly covered by the spray, and there are unsprayed plants on 

 which they can oviposit. 



Conclusions 



1. Tipburn or hopperbuni of the potato is produced through the 

 agency of Empoasca mail. 



2. All nymphal stages of the leafhopper are capable of producing 

 symptoms of the disease. 



