Plum, Potato. 345 



one-twenty-fifth of an inch in length ; they are very narrow, 

 flat, and of a brown color. About the first of April these 

 minute scales move about and soon fasten themselves, gener- 

 ally to the under side of the small branches. They increase 

 rapidly in size, so that in two months they are from two to 

 three-sixteenths of an inch in length, and nearly circular in 

 outline. At this time eggs are abundantly produced under 

 the large brown scales, and by the first of July the young in- 

 sects may be seen crawling over the branches. They pass oil 

 to the under side of the leaves, where they establish themselves 

 near the larger veins. Here they remain until the latter part 

 of August, when they return to the branches. The affected 

 leaves make little growth and look unhealthy; and although 

 the scales have increased but little in size, so much sap has 

 been removed that the trees make but little growth and the 

 fruit is dwarfed. When the insects return to the branches 

 in the fall they are of a rich brown color, and but one-twenty- 

 fifth of an inch in length ; in this form they hibernate, and the 

 following spring they again become active. 



Treatment. In the fall, as soon as the foliage has fallen, spray 

 the trees with the Hubbard-Riley kerosene emulsion diluted 

 with four parts of water. A weaker emulsion will not be 

 effective, and a stronger one may injure the trees. If this 

 work is thoroughly done, the pest can be practically extermi- 

 nated. The application may be made any time from Novem- 

 ber to April. During the summer months the foliage interferes 

 with the proper application of the spray, and the emulsion can- 

 not be applied to the leaves with safety. 



Slug. See under CHERRY. 



POPLAR. 

 See COTTONWOOD. 



POTATO. 

 FUNGOUS DISEASES. 



Early Blight (Macrosporium Solani, E. & M.). Description. 

 The early blight of potatoes is not yet fully understood, but 

 much of the early dying of the leaves is no doubt caused by the 

 fungus mentioned. Observations tend to show that the injuries 

 caused by the flea-beetle frequently serve as starting-points for the 

 disease (Fig. 79). Around the little holes made by these insects, 



