PLANT-DISEASES. 73 



soon as the fruit is picked. Destroy all affected leaves. 

 The leaves are easily destroyed without injury to the plants 

 by quickly burning off a thin layer of straw which is spread 

 over the patch after the fruit is off. Where the disease is 

 feared, the best treatment, in general, is to fruit the planta- 

 tion but once. 



MILDEW (Sphcerotheca Castagnei, L6v.). A whitish cobweb- 

 like mildew spreading over the fruit and leaves and causing 

 the latter to curl as if wilted. 



Remedies. If the disease is discovered early enough, 

 some liquid fungicide, as ammoniacal carbonate of copper or 

 Bordeaux mixture, should be employed. Sulphur scattered 

 upon the foliage and upon the soil about the plants is said 

 to check the disease. 



Sweet-Potato. BLACK-ROT (Ceratocystis fimbriata, Ell. & 

 Hals.). A dry-rot of the tuber, and a black rust upon 

 the stems. Upon the tuber it appears in large scab-like 

 patches, and is usually evident at digging time. It may 

 appear upon the young plants in the hotbed and persist 

 upon them throughout the season. 



Remedies. Rotation of crops. Spray the young plants, 

 if attack is feared, with copper fungicides. 



DRY-ROT (Phoma .Batatce, Ell. & Hals.). The upper end of 

 the tuber becomes dry and wrinkled and bears a multitude 

 of pimples, and its flesh becomes dry and powdery. 

 Preventive. Destroy all affected tubers. 



LEAF-BLIGHT (Phyllosticta bataticola, E. &M.). Produces 

 white, dead patches upon the leaves. 

 Remedy. Spray with some of the copper fungicides. 



SCURF (Monilochcetes infuscans, Ell. & Hals.). The whole 

 surface of the potato becomes scurfy, and it causes the 

 tuber to shrink. 



Preventive. Use only healthy potatoes for seed. 



SOFT- ROT (Rhizopus nigricans, Ehr.). The tubers rot with 

 a soft and putrid decay. It is most destructive after the 

 potatoes are stored. 



Preventives. Store in a well-ventilated, artificially 



