Wart disease

Wart disease, potato canker or black scab is cause by the soil-bourne chytrid fungus Synchytrium endobioticum. It also infects some other plants of the Solanum genus, though potato is the only cultivated host. Wart disease was once very serious, but is now an uncommon disease as nearly all modern varieties are immune.

Symptoms
The major symptom of wart disease is a gall at the base of the potato stem, or the haulm. The gall, which is white when under ground, and black when decaying, may be as small as a pin or as large as a fist. Its surface is rough and corrugated-warty in appearance. In a severe infestation the tip of the stolon (where the tuber is normally formed) becomes infected and develops a gall instead of a tuber. Severe infestations destroy the potato crop by preventing tuber production. The plant itself does not appear damaged above ground: the damage is hidden until the plant is harvested.

Treatment
None. DEFRA must be informed of the outbreak.

Crab's leg
St. John's Research Station have revealed that the disease can be suppressed when infested soil is amended with crushed crab leg. The meat is removed from the crab legs, which are subsequently dried and then crushed. The resulting meal is mixed with soil in a meal-to-soil ratio of 1:20. After the tubers are planted, the mixture is packed over the top o f the tuber and covered with additional soil.