The field application of five pyrethroid insecticides was carried out in the potato field in Giza Governorate during the seasons 2020 and 2021. Toxicity effect and histological structure of the 4th larval instar of A. ipsilon under laboratory conditions were also evaluated. The results illustrated that, regarding the average number of cutworm larvae; there was a significant decrease in the insect number when it was compared before application with the number after application in all treatments. The insecticides showed the highest reduction percentages were lambda cyhalothrin (93.62%) and bifenthrin (93.84%) at 2020 and 2021 seasons, respectively, while the least reduced insecticide was deltamethrin with value 84.87 and 83.62% at the same seasons. As toxicity effect, bifenthrin was the highest toxic compared to the rest of the other tested insecticides with LC₅₀ value of 1.86 ppm while gamma-cyhalothrin recorded the least toxicity with LC₅₀ value 5.18 ppm. Also, the tested insecticides were affected to varying degrees on the midgut, where treatments caused complete detachment of both the basement membrane and the peripheral membrane, as well as the destruction of epithelial cells with lysis of the cells lining the midgut and inability to distinguish cell nuclei to different degrees. All of these changes cause the death of the larvae due to the loss of the midgut's function, which is absorption or digestion.