Disease Comparison

Comparison of Potato Diseases

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External Symptoms

Internal Symptoms

Spread in Storage

Main Source

ROTS

Bacterial Soft Rot

slimy, tan spots around wounds or at stem end

slimy, soft rot with dark borders

yes

vine, soil

Leak

dark, large areas; smell; papery shell

liquidized, cavities rancid smell

no

soil

Pink Rot

dark areas near stem end, around eyes and pores

pink area afer cutting; slight odor

yes

soil

Dry Rot

dry decay around wounds fungal growth possibly seen

dry cavity from wounds; possible ring discoloration

no

vine, soil

NON-Rotting

Black Dot

shiny, brownish areas, reddish on attached stolon

none

yes

seed, debris

Silver Scurf

shiny, silvery areas

none

yes

seed

Common Scab

rough, round surface areas to brown pits

pits extend into tuber

no

soil, seed?

Early Blight

brownish-blac k, irregular sunken areas

shallow, dry and brown below sunken areas

yes

lifting

Black Pit

narrow, deep, black pits

pits extend into tuber

?

?

Late Blight

brown areas turning black and sinking (depressions)

reddish brown below discolored areas

Z

leaching

Black Scurf

black, hard, small spots

none

no

soil

Early Dying

none; pink eye may occur

vascular discoloration

no

vine, soil