V. THE CUCUMBER FLEA-BEETLE AS THE CAUSE 

 OF " PIMPLY " POTATOES.* 



Summary. 



The cause of the trouble known as '' pimply " potatoes has 

 been definitely determined. Minute, slender, white grubs have 

 been found boring into the tubers, roots and rootstocks of the 

 potato during the growing season. The pupa3 of these grubs 

 have been found in connection with them. The grubs and pupaj 

 have been proven to be the eai'ly stages of the common cucumber 

 flea-beetle, a very injurious insect, the life history of which has 

 heretofore been imperfectly known. The wound made by the 

 boring of the grub results in the formation of a " sliver," but a 

 " pimple " may or may not be produced, depending, probably, 

 upon the stage of growth of the tuber at the time the wound 

 is made. 



The most practical method of preventing the " pimply " potato 

 trouble is to protect the foliage against the attacks of flea-beetles 

 by thorough spraying with Bordeaux mixture. 



Seedling plants of various kinds suffer severely from the at- 

 tacks of flea-beetles. Bordeaux mixture to which a small quan- 

 tity of Paris green has been added is exceedingly efficient as a 

 preventive of these attacks, provided that it is apijlied thor- 

 oughly and frequently. i 



Relation of the Cucumuer Flea-Bketle f to *' Pimply " 



Potatoes. 



In a previous bulletin| of this Station there was given a brief 

 account of a potato trouble in which small, scurfy, pimple-like 

 elevations are scattered irregularly over the surface of the tuber. 

 Underneath each of the elevations there is a brown, sliver-like 

 body, comjtosed of corky tissue and about one-ninth of an inch 

 in length, penet ruling into the white flesh of the tuber. 



• Publiihed also as Bulletin No. 113. 



+ Crepidodera (Epitrix) cucumeris Ilarr. 



t Xew York Exp. Sta., Bulletin No. 101, pp. 84-85 ; also p. 511 of this Report. 



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