Jasmonic and salicylic acids (JA and SA) are plant phytohormones that play key roles in resistance/tolerance to biotic and abiotic stresses and interact with the other families of phytohormones to modulate growth and development. Understanding these PGRs and their roles has given modern agriculture new tools to fight diseases and pests, reduce the build-up of resistance to fungicidal and insecticidal active ingredients and enhance crop tolerance to a wide range of abiotic stresses, such as wet, dry, cold and hot.