Question
Over the years i have seen  my or friend's calla lily's begin to develope yellow leaves, one by one, that are dying at the base. I can find no bugs, no fungus or rot, but the plant surely dies by turing into a slimy dissolved mess from the base upwards. I cut, but the next one begins.  jon

Answer
Hi Jon,
Thanx for your question.  What you are describing sounds a lot like bacterial soft rot (Erwinia carotovara var. aroideae).  This disease affects the base of the plant and sometimes the corm but not the feeding roots.  The soft rot begins at the base of the plant and travels up the leaves and the base becomes slimy.  Eventually, the corm is attacked and then finally the roots may become affected.  Dig up damaged roots and discard.  Don't plant anymore calla lilies in that spot.  Treat dormant corms with antifungal powders.  I hope this helps.
Tom