A method for controlling insect pests on a plant is provided. The method includes applying to the plant and/or to the insect pests a combination comprising: a nitrogen-bearing macrocyclic compound which is a photosensitizer that generates reactive oxygen species in the presence of light, the photosensitizer being selected from the group consisting of a porphyrin, a reduced porphyrin and a mixture thereof; and a chelating agent which is an aminopolycarboxylic acid compound or an agriculturally acceptable salt thereof; and exposing the plant to light in the presence of the insect pests to activate the nitrogen-bearing macrocyclic compound and generate reactive oxygen species.