Characteristics of Diseases. 



Late blight rot or potato disease is notorious as the cause of the potato famine 

 of 1845 in Ireland. It is quite prevalent in moist autumns in Eastern Canada 

 when it attacks the leaves and stems, thence invading the tubers. In the stored, 

 infected potatoes, dry rot is the form taken by the disease. The skin exhibits 

 darker brown, slightly shrunken areas, more than normally hard. Cut across, the 

 flesh appears mottled with brown which spreads around the margin, gradually 

 involving the whole tuber in decay. Soft rots may accompany dry rot. It must 

 be remembered that infected seed potatoes carry the fimgus with them to the field, 

 to there reinfect the new crop, should the seed grow. Estimated losses from late 

 blight and dry rot are, United States, $36,000,000 annually; New York, $10,- 

 000,000 for 1912; for Prince Edward Island, $1,000,000 in 1915, when the disease 

 was more than usually severe, and the damage done was on the same or a larger 

 scale over Eastern Canada. 



Fusarium Wilt and Dry Rot. 



This "imperfect" fungus (Fusarium sp. ) causes the trouble known as 

 dry rot, end rot and bundle blighting. Infected seed gives seemingly normal plants 

 which, however, wilt about blossoming time, and the vascular bundles of the stem 

 are discolored. The roots are affected, and the young tubers often attacked at 

 the stem end. with stem end rot. The fungus can rot potatoes under dry condi- 

 tions but grows faster if it enters through wounds. It causes little injury at i2° 

 to 36° F. The dry rot is a brown, compact, firm rot, without a foul odor. Cavities 

 are often present, in which mycelium grows plentifully. Careful handling in 

 digging, and storing is advised to avoid cuts and bruises. Clean and very cool 

 storage reduces danger of diseases. 



Wet or Soft Rots. 



These decays are caused by bacteria, by a Sclerotinia fungus, and by black 

 or blue molds, but potatoes are rarely attacked, except as a secondary infection. 

 Taubenhaus describes a black rot or jelly end rot as caused by Fusarium radici- 

 cola W'oll, "The stem end soft rots. The disease progresses inwards until the entire 

 tuber within the skin becomes soft and jelly-like in consistency. The trouble is 

 confined mostly to Idaho, Rural, and Pearl ' varieties)."' 



Soft Rot and Black Leg. 



Bacillus solanisaprus (Harrison) causes a drooping and shrivelling of leaves 

 and stem, with black areas on petioles and stems near the ground. On tubers, 

 "the skin shows reddish-brown discolored areas, something like a bruise, with a 

 firm consistency," the flesh beneath turns soft. A black line marks off the healthy 

 and diseased areas. "In the final stage the potato becomes a mass of black soft 

 pulp". In storage, the rot spreads. Seed potatoes carry over the disease, and the 



