|
Tumours, due to cell proliferation, of variable size (from a few mm to the size of a fist), develop on :
the lenticles,
the stolons,
parts of the stem under the ground.
Attacks are mainly below ground level, however, under very damp conditions, they can also be observed above ground.
Unlike powdery scab or root-knot nematodes, the tumours never form on the roots.
The tumours are initially whitish, turning black later on and releasing a black spore powder. The tumours can turn green if they are exposed to light.
The disease can develop during storage.
|
 |