What is a plant-incorporated protectant?

Plant-incorporated protectants are pesticidal substances formed and used by the living plant, typically to protect the plant from pests, like insects, viruses, and fungi.  Plant-incorporated protectants can happen naturally in plants, or can be introduced into plants by either the conventional breeding of sexually compatible plants or by the techniques of modern biology (e.g. genetic engineering).  For instance, the Cry proteins from Bacillus thuringensis (Bt) bacteria can be introduced into plants, which then make the pesticidal protein and give the plant with resistance to Lepidopteran insects (e.g. the European corn borer larvae).  Plant-incorporated protectants have also been referred to as plant-pesticides.