The invention is an animal repellant composition containing one or more toxins, including for example one or more alkaloids isolated from for example, one or more members of the family Narcissus, and optionally containing one or more polymers, including for example one or more bioerodible polymers and/or more non-absorbable polymers. The animal repellant composition is useful for repelling animals from vegetation and for rendering vegetation unpalatable to animals. The invention also includes methods for repelling animals, as well as methods for treating vegetation to render the vegetation unpalatable to animals, such animals including for example, deer, voles, moles, ground hogs, mice, rats, rodents, raccoons, nematodes, larvae, worms, fungi, molds, bacteria, vegetative organisms, and insects. A suberin-polymer-repellant chemical complex and a method for treating damaged vegetation are also disclosed. Various other systems and methods for complexing biopolymers, toxins, and polymers for treating plants, microbially inactivating the bioburden of vegetation, and for repelling animals are disclosed.