although insects can be a problem, by far the biggest killer of carnivorous plants (besides human maltreatment) is grey mold ("botrytis cinerea"). this thrives under warm, humid conditions and can be a real problem in winter. to some extent, temperate carnivorous plants can be protected from this pathogen by ensuring that they are kept cool and well ventilated in winter and that any dead leaves are removed promptly. if this fails, a fungicide is in order.