Spindle Tuber Viroid

Symptoms -- Infected plants are erect and slightly stunted. They are darker green that normal. Leaf tips are pointed upward, best seen in hot weather. Tubers are elongated with pointy ends and may have cracking.

Technically the pathogen is not a virus but a viroid that is a virus without its protective coat.

Spread is through physical contact and by cutting knives.


Purple Top and Aster Yellows, Haywire, and others

Purple Top / Aster Yellows -- Plants have short, vigorous secondary branching. Aerial tubers are common. Young leaves at top will roll at their base that may also appear pink or purple or yellow. Tubers from infected plants are flabby and produce hair sprouts as might be seen from excess heat (heat sprouting) and psyllid toxin. See Picture.

Haywire -- Plants are severely stunted and form a rosette. Leaves are rough and stiff, erect and rolled, pointed, and slightly yellow. Seed pieces from infected plants with produce the "little tuber disorder" as seen in picture.
The mycoplasmas are spread via leafhoppers.

Control is done through certification, roguing, leafhopper control and control of host weeds.

Witches' Broom

Symptoms -- Plants are severely stunted and appear bushy due to loss of apical dominance on vine. Leaves turn light green with reddish-yellow margins. Seed tubers from infected plants sprout producing a very bushy and erect plant. There are many sprouts per eye. Stolons are long and tuber chaining is seen.

Spread is via various leafhoppers. The mycoplasma is passed on non-persistently by leafhoppers that prefer other hosts than potato. These leafhoppers are unable to pick up the mycoplasma from potato so the presence of another infected host is required.

Control involves aphid control, and planting away from perennial legumes such as alfalfa or control of perennial legume weeds.


 Little tuber disorder

Little tuber disorder


Purple top disease

Purple top disease