Kumara, a member of the sweet potato family, can produce toxins in response to injury, insect attack and other stress. The most common toxin, ipomeamarone, can make the kumara taste bitter. There have been reports of cattle deaths after they have eaten mouldy kumara. The toxin levels are usually highest near the area of damage. It is recommended that any damaged parts on kumara are removed before cooking. Do not eat it if it tastes bitter after cooking. See more about Natural toxins in food