Sublethal Effects of Triazophos on the Life Table Parameters ofSogatella furcifera(Hemiptera: Delphacidae)

Abstract

Sogatella furcifera (Horváth) (Hemiptera: Delphacidae), the white-backed planthopper, is a serious pest insect in rice (Poales: Poaceae) paddy fields in China and elsewhere in Asia, and it is primarily controlled using chemical methods. Triazophos is a broad-spectrum, non-systemic organophosphorus insecticide used for pest control in rice paddy fields. In this paper, we examined the sublethal effects of triazophos on nymphal duration and life table parameters of S. furcifera in the laboratory. The results showed that sublethal concentrations of triazophos could significantly prolong nymphal duration in S. furcifera. Relative to the control, exposure to LC10 and LC25 extended the nymphal period by 0.92 and 3.16 d, respectively. A fitness analysis was performed by constructing a life table in the F1 generation and showed that sublethal concentrations of triazophos could stimulate reproduction in S. furcifera populations. Various life table parameters were depressed under sublethal concentrations of triazophos, but fecundity was the exception. The fecundity rates (eggs per female) in LC10 and LC25 triazophos treatments were 116.2 and 131.9%, respectively, that of the control in the 2nd generation. The relative fitness of S. furcifera planthoppers treated with LC10 and LC25 of triazophos was 77.6 and 63.6%, respectively, compared with the control. Sublethal concentrations of triazophos inhibited population growth relative to the control group based on the predicted number of offspring. However, the possibility of oviposition stimulation at sublethal concentrations should be considered carefully if triazophos is applied to control white-backed planthoppers and other rice pests in a rice field habitat.