Diseases

Potato:

Bacterial Soft Rot
Black Dot
Common Scab
Early Blight
Fusarium Dry Rot
Late Blight
Pink Rot
Powdery Scab
Rhizoctonia/Stem and Stolon Canker
Silver Scurf
Leafroll/Tuber Net Necrosis

Onion:

Bacterial Soft Rot
Black Mold
Blue Mold
Botrytis Leafspot
Downey Mildew
Iris Yellow Spot
Onion Pink Rot
Sour Skin
White Rot

Sweet Potato:

Black Rot
Charcoal Rot (end of page)
Java Black Rot (4th item)
Pox, Streptomyces soil rot
Rhizopus Soft Rot (3rd item)
Root Rot
Root-knot Nematode
Sclerotial Blight