Fractal-Divine Seeds

My guess would also be a fungus or bug in that stem. Keeping it won't bring any positive as it is already dead, so I would 2nd Lerome's advice to chop and inspect it. Just chop a bit away from your main stalk so the wound is not on the stem of the plant, creating a new opening where fungus can infect the plant. Do it in the morning on a dry day so the wound can dry as fast as possible.