Looks to me like Botrytis (gray mold). -Mark

The chance of success with a cutting that small is low, BUT what have you got to lose!!!! Give a shot. You should let the cut end callous over before rooting. I wait a week. Mike

Hi Tiffany, Thanks for your reply. Such a shame but that was as I suspected. It is not in a highly sunny area of the house, but not dark either, but good to know that perhaps more sun and light was needed. The top peice initially broke off at the rotten point, so I cut further up until I reached a part which was not rotten, it was not green, but rather white (but this time firm and looked sort of normal, not like the brown or creamy mushy stuff at the base/trunk). Thanks, Danielle

Friday I brought home a gorgeous and enormous philodendron selloum that had just been unloaded from the delivery truck (oops. Now I know to avoid brand new stock). Saturday night, I noticed a tiny stem going to mush. Sunday, emergency surgery, removing 2 outlying clumps because of stem rot. The roots seemed strong. Monday, I removed another small clump. Tuesday, a new leaf unfurled from the main trunk, but it seems unusually thin. The leaves and stems of the primary trunk have been unaffected. I've coated all pruned tissue liberally with cinnamon or cinnamon-canola paste. It's under bright 5000K lights, in a well-ventilated area, in a well-draining mix. Unfortunately, it's been raining all week and the indoor humidity is in the 60% range, but there's nothing I can do about that but wait for the rain to pass and humidity to plummet back to normal levels. Obviously the plant is in quarantine. I do understand that survival chances are nil if it's systemic rot instead of only foliar, but the articles I've found don't say how to tell. I suppose if it survives the week, then it has a chance...? Does anyone have any experience bringing a philodendron through an infection like this successfully? The remaining plant looks strong (but for the thin new leaf), but I've never dealt with anything like this before. Thanks in advance.