Insecticide Susceptibility and Detoxification Enzyme Activity of Frankliniella occidentalis under Three Habitat Conditions

Abstract

<i>Frankliniella occidentalis</i> is a highly destructive and invasive agricultural pest that has developed resistance to a variety of insecticide classes. Different planting structures and insecticide use frequency can directly affect the resistance development of <i>F. occidentalis</i>. In this study, the susceptibility of three field strains of <i>F. occidentalis</i>, collected over one year (April to November) from three habitat conditions (facility agriculture area, FA; open field crop area, OF; agroforestry intersection area, AI), to spinetoram, spinosad, emamectin benzoate, chlorfenapyr, acetamiprid, and imidacloprid were monitored and compared. At the same time, the detoxification enzyme activity of <i>F. occidentalis</i> in different habitats was determined. The results showed that the susceptibility of the <i>F. occidentalis</i> population in FA was significantly lower than that of populations from OF and AI. Among them, the <i>F. occidentalis</i> population in FA had developed low levels of resistance to spinetoram (RR = 9.18-fold), emamectin benzoate (RR = 5.47-fold), chlorfenapyr (RR = 6.67-fold), and acetamiprid (RR = 7.49-fold), and had developed moderate level resistance to imidacloprid (RR = 11.67-fold), while still being relatively sensitive to spinosad. The population of <i>F. occidentalis</i> from OF had developed low level resistance to spinetoram (RR = 5.24-fold) but was still relatively sensitive to the other five insecticides. The resistance of <i>F. occidentalis</i> from AI to six insecticides was at relatively sensitive levels. The results of the enzyme activities of detoxification enzymes, including carboxylesterase (CarE), glutathione S-transferase (GST), acetylcholinesterase (AChE), and the cytochrome P450 enzyme system (CYP450), revealed that the activities of the FA population of <i>F. occidentalis</i> were significantly higher than those of the other two populations. The change of CarE activity in <i>F. occidentalis</i> was consistent with that of spinetoram resistance, indicating that CarE may be involved in the metabolic resistance of <i>F. occidentalis</i> to spinetoram. Among the three populations, the resistance and detoxification enzyme activities of <i>F. occidentalis</i> of the FA population to six insecticides were higher than those of the other two populations. Our findings, along with other strategies, are expected to help with the resistance management of <i>F. occidentalis</i> in different habitats.