BULLETIN No. 211. 



POTATO FLEA-BEETLE*. 



O. A. JOHANNSEN. 



THE FLEA BEETLE AND EARLY BLIGHT. 



The flea beetle (Epitrix cuciuiieris) is, next to the Colorado 

 potato beetle, the most destructive of the annually recurrent 

 insects on the foliage of the potato in Maine. The insect eats 

 minute holes in the leaf giving it a dotted appearance like a 

 pepper box cover (Fig. 19). Sometimes the damage done by 

 this pest is very marked as was the case of a small unsprayed 

 field in Orono the past year when the plan.ts were entirely 

 killed before July 10. But the danger to the plant is not re- 

 stricted to what the insect alone can do, for it is generally ac- 

 knowledged that early blight attacks injured leaves more readily 

 than healthy ones and the punctures made by the insect serve 

 as points of entrance for the germ tubes of the spores of the 

 fungus. The insects themselves are also in all probability 

 active agents in spreading the disease by carrying the spores 

 from plant to plant on their bodies. Early blight is widespread 

 and now very destructive in that it attacks and weakens the 

 plant at a critical period, thus checking the development of the 

 tubers. It is confined to the foliage and is not known to cause 

 rot. Early blight first appears as small brown spots, frequently 

 surrounding flea beetle punctures, scattered over the older 

 leaves. These spots slowly enlarge and frequently become some- 

 what angular in shape from the fact that they stop on reaching 

 a leaf vein. There is usually a sharp boundary between the 

 healthy green of the leaf and the spot, although a badly spotted 

 leaf will have a decidedly yellow appearance over its entire 

 surface. Close inspection of the early blight spots will usually 

 show concentric lines. Early blight may occur alone or asso- 

 ciated with late blic-ht. 



^Papers from the "Maine AgriculUiral Experiment Station : Ento- 

 molo.sy No. 64. 



