Assessment of detoxification enzyme activities and hemocyte examination of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) in response to Mentha pulegium and Artemisia camphorata extracts

Abstract The interest in botanical insecticides has surged due to environmental apprehensions and insect resistance to synthetic insecticides. In this study, we explored the insecticidal, biochemical, and physiological effects of Mentha pulegium essential oil (EO) and Artemisia camphorata methanol extract (ME) on the fourth-instar larvae of Spodoptera littoralis . By GC–MS analysis, the main compounds identified in M. pulegium EO were menthone (22.45%), 1,8-cineole or eucalyptol (19.37%), and pulegone (8.67%). The abundant flavonoid compounds were apigenin, luteolin, quercetin, and naringin, whereas the abundant phenolic compounds were 4-hydroxybenzoic, ferulic, and chlorogenic acids in A. camphorata ME after analysis by HPLC. The LC 50 values after 24 h of S. littoralis treatment with M. pulegium EO, A. camphorata , and novaluron were 4458.3, 7349.9, and 9.8 mg/L, whereas the LC 50 values after 48 h of treatment were 2495.3, 4024.5, and 7.7 mg/L, respectively. The activities of mixed-function oxidase, α and β-esterases, and glutathione S -transferase were significantly increased in S. littoralis larvae after 24 and 48 h of treatment with LC 25 and LC 50 concentrations of novaluron, M. pulegium EO, and A. camphorata ME. The mean number of prohemocytes, granulocytes, and plasmatocyte cells was significantly decreased at 24, 48 and 72 h of treatment with LC 25 of M. pulegium EO and A. camphorata ME. In contrast, the number of oenocytes and spherulocytes was increased compared to the control. On the other hand, novaluron caused a significant decrease in all hemocyte numbers. The hemocyte surface areas increased dramatically in all hemocyte types after treatment with M. pulegium EO and A. camphorata ME. In contrast, hemocyte surface areas significantly decreased after novaluron treatment compared to the control. These findings suggest that M. pulegium and A. camphorata may be eco-friendly alternatives for synthetic insecticides in S. littoralis control.