Root rot or wet rot can affect euphorbias if the soil remains too wet for a long time, or if too much water is given too quickly after the root ball has dried out completely in the rest period. Weakened plants can easily succumb to fusarium fungus, leading to root rot. The disease manifests itself with brown discolouration of the plant neck, spreading to the whole plant, the inside of which turns to a soft, colourless jelly.

The only cure for root rot is to cut off the still unaffected parts of the plant, but generally this only works during the early stages of the disease.