Abstract
Synthetic and natural insecticides have successfully controlled the Indian meal moth (Plodia interpunctella Hübner). However, little is known about how Indian meal moth reacts in a stressed environment caused by synthetic and botanical insecticides. Therefore, this study compared the effects of dichlorvos (DDVP) and ginger (Zingiber officinale L.) rhizome extract oil on larval and adult mortality, hatchability and adult emergence, and on neurotransmitters and digestive enzymes of Indian meal moth under laboratory conditions of 75 ± 5% relative humidity and 25 ± 5 °C. The insects were exposed to different concentrations of 0.1, 0.2, 0.3, 0.4, and 0.5% of dichlorvos and ginger extract oil for 96 h. Ginger rhizome extract oil caused 100% mortality in newly emerged adult Indian meal moths within 96 h at all concentrations. DDVP and ginger extract oil were ineffective against the third instar larval stage of the Indian meal moth, at varying concentrations that caused adult mortality. DDVP and ginger rhizome extract oil significantly affected digestive enzymes and acetylcholinesterase activities at lethal concentrations used in treatment. Protease activity was significantly increased in larvae exposed to extract oil than DDVP. Acetylcholinesterase activities in the adult insects exposed to maize grains treated with DDVP were higher than those exposed to maize treated with ginger extract oil. DDVP and the ginger extract oil have significant effects on the digestive enzymes. Nevertheless, ginger extract oil increased larval protease activity more than DDVP.