The present disclosure describes a formulation including a nanoparticle including a polymer-associated mectin and/or milbemycin compounds with an average diameter of between about 1 nm and about 500 nm; wherein the polymer is a polyelectrolyte, and a dispersant or a wetting agent. The disclosure describes various formulations and formulating agents that can be included in the formulations. Additionally, the disclosure describes application to various plants and pests as well as advantages of the disclosed formulations.