REPORT OF THE SOCIETY 61 



deal of damage, although in some parts of the States does as much damage 

 as Late Blight in Canada, is characterized by the target marked spots of 

 the leaves. The spots are usually brown and have concentric rings or marks. 

 This disease is also controlled by spraying with Bordeaux. 



Rhizoctonia, according to reports from many sections of Canada did con- 

 siderable damage. Rhizoctonia is known by many symptoms. The leaves 

 usually have a slight yellowish tinge, form in cluster, hence the name of 

 Rosette which it often goes under. There is also a curl of the leaves. In 

 bad cases aerial tubers will form, and in all cases t"he tubers will form 

 very close around the stem near the surface, and will be small. I have seen 

 samples where there were hundreds of potatoes the size of tip of my little 

 finger, hence another name that Rhizoctonia often goes under, "Little 

 Potato Disease." These symptoms are similar to other stem diseases, 

 but on pulling the stem lesion will be noted on the stem just below the ground 

 These lesions are in the form of cracks covered with brown mycelium 

 giving a brown appearance. This distinguishes Rhizoctonia from all other 

 diseases. The disease winters over on the potato in black spots or scurf. 

 It is controlled by selection and treatment of seed. 



Blackleg is a bacterial disease causing a wilting and turning yellow of 

 the leaves, and a blackening of the stem at and below the ground. The 

 plant will fall completely over and die. The tubers of an infected plant 

 will show a discolouration in the vascular ring in the early stage and later 

 a complete blackening and softening of the inside of the potato. Controlled 

 by the selection of good seed; all discoloured seed should be discarded 

 when cutting and also throwing out discarded hills in the growing crop. 



Fiisarium Wilt also causes discolouration and wilting of the leaves, 

 but characteristic of the disease is the discolouration of the vascular system 

 of the stem just below the ground. The stem when cut shows a brownish 

 ring or markings in the vascular bundles. It is controlled as for Blackleg. 



There are also three diseases of unknown origin, that do not show in 

 the seed tuber but do considerable damage to crops, namely. Mosaic disease, 

 Curly Dwarf and Leaf Roll. 



Mosaic is characterised by the mottled and puckered appearance of 

 the leaf. The leaf is normal except for the lighter spots or blotches which 

 are usually somewhat puckered. 



Curly Dwarf usually shows a dwarfing and rolling of the leaves. The 

 stems, petioles and veins all seem to be shortened, giving a puckered compact- 

 ness to the leaf. There is a tendency for excessive branching causing a 

 distinct clustering. 



