Quote Originally Posted by ksriramkumar View Post
blacking of leaf tip could be a sign of lack of calcium. The blacking in the second picture appears on the bulbs and base of the leaf and that looks like a black rot to me.
I am not sure about leaf tip problem... it can be caused by overfeeding. I agree with you regarding second picture: it is a rot. However, it looks to me more like a pseudobulb rot which affects oldest growth first and occurs mostly in colder and darker conditions. Black rot usually starts with youngest growths and occurs when it is warm and humid. Lack of air movement is a very important contributing factor, too. Anyway, all affected p-bulbs should be removed. Standard 3% hydrogen peroxide can be used to clean rhizome.