Insect barriers for building structures include rigid foam sheets and sheets of film or mesh formed of polymer material impregnated throughout with a synthetic pyrethroid insecticide such as permethrin. Foam sheets are applied to exterior and interior surfaces of foundation walls to provide both thermal and insect barrier functions. Film and/or mesh sheets are positioned around exterior and interior perimeters of foundation walls to form skirts serving as insect barriers. Plant containers for containing growing plants are formed of polymer material impregnated throughout with a synthetic pyrethroid insecticide. Agricultural mulching film for covering the soil beneath and around a growing plant is formed of polymer material impregnated throughout with synthetic pyrethroid insecticide.