Nanoparticle (e.g., quantum dot) compositions and methods for delivery of substances (e.g., microbicies, fungicides, pesticides, therapeutic agents, biologics, diagnostic agents, dyes, marker substances or tags, etc.) to desired locations within plants or animals. In some embodiments, the quantum dot or naoparticle may be substantially free of cadmiun. In some embodiments, the methods may be employed to prevent to treat fungus or fungus-like infections in pains, such as agricultural crops.
