Harpin protein is produced in nature by certain bacterial plant pathogens. When sprayed on a plant, it elicits a natural defense mechanism within the plant, very much as the human immune system is started up when a bad germ gets into the body.

The Harpin protein, when sprayed on the plant, elicits a protective response in the plant that makes it resistant to a wide range of fungal, bacterial, and viral diseases. With no expected adverse effects to human health or the environment, use of Harpin protein has the potential to substantially reduce use of more toxic pesticides.