Inhibitory Effect of PBO and DEF on Detoxification Mechanisms Involved in Deltamethrin Resistance in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Benin, West Africa

Pyrethroid resistance has been a growing problem in the management of Helicoverpa armigera populations in West Africa; with the metabolic resistance considered Inhibitory Effect of PBO and DEF on Detoxification Mechanisms Involved in Deltamethrin Resistance in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Benin, West Africa 386 as a prominent resistance pathway. Formulating insecticides with synergists that counteract metabolic resistance might help overcome insecticides resistance in this pest. This study aimed to evaluate the metabolic enzymes involved in the resistance of H. armigera to deltamethrin. To assess the mechanism involved in the H. armigera resistance, we evaluated the effect of two synergists (piperonyl butoxide (PBO) and S,S,S-tributyl phosphorotrithioate (DEF) on deltamethrin efficacy in four resistant strains. A high synergism ratio (SR) of the three top resistant field strains Allada (RF=372); Malanville (RF=476) and Djidja (RF=516) was revealed when PBO was used with deltamethrin (Allada SR=128; Malanville SR=98 and Djidja SR=243) compare to a moderate resistance locality (Kassakou: RF= 13; SR= 25). Whereas, application of DEF had no synergistic effect in the farms located in the northern part of Benin (Kassakou, Malanville: SR=1) compare to the southern localities where the farmers used pyrethroids insecticides in several crops production (Djidja SR= 206; Allada SR= 8). The synergism data collected strongly suggest that detoxification enzymes play a significant role in the resistance of H. armigera. The development and use of safe metabolic synergists that suppress detoxification enzymes offers an interesting avenue for the management of insecticideresistant field populations.