Abstract:

【Aim】 Emamectin benzoate (EMB) is a novel antibiotic bio-derived insecticide and highly efficient in controlling lepidopteran pests. This study aims to investigate the sublethal effects of EMB on the rice pest of Hemiptera, Sogatella furcifera. 【Methods】 Using rice stem-dipping method, we first determined the LC₁₀, LC₂₅ and LC₅₀ values of EMB against the 3rd instar nymphs of S. furcifera reared for 72 h on the rice seedlings treated with EMB at different concentrations. The 3rd instar nymphs of S. furcifera were reared on rice seedlings treated with EMB at the LC₁₀, LC₂₅ and LC₅₀ concentrations for 48 h through the rice stem-dipping method. The female adult longevity and the number of eggs laid per female of the F₀ generation were determined. The duration of egg and the 1st-5th instar nymphs, adult longevity, pre-adult duration, total developmental duration, adult pre-oviposition period, adult total preoviposition period, and the number of eggs laid per female of the F₁ generation were counted to construct the age-stage, two-sex life table. The population dynamics of S. furcifera were predicted in 60 d by using Timing-MSChart software. 【Results】 The LC₅₀, L_C25 and LC₁₀ values of EMB against the 3rd instar nymphs of S. furcifera were 0.831, 0.222 and 0.068 mg/L, respectively, at 72 h after treatment. In the F₀ generation, S. furcifera female adults treated with EMB at the concentrations of LC₁₀, LC₂₅ and LC₅₀ had reduced average longevity by 7.19%, 24.81% and 34.21%, and decreased number of eggs laid per female by 22.24%, 31.22% and 41.53%, respectively, compared with the control group. EMB at the LC₂₅ concentration significantly prolonged the 5th instar female nymphal duration of the F₁ generation and EMB at the LC₅₀ concentration significantly prolonged the male adult longevity and total developmental duration of the F₁ generation compared with the control group. EMB at the LC₂₅ and LC₅₀ concentrations significantly prolonged the adult pre-oviposition period and total pre-oviposition period of the F₁ generation of S. furcifera, and significantly reduced the intrinsic rate of increase (r) and finite rate of increase (λ) of the F₁ generation compared with the control group. EMB at the LC₅₀ concentration significantly decreased the net reproductive rate (R₀) of the F1 generation and EMB at the LC₂₅ concentration significantly prolonged the mean generation time (T) of the F₁ generation compared with the control group. The three sublethal concentrations (LC₁₀, LC₂₅ and LC₅₀) of EMB significantly inhibited the population growth of S. furcifera. 【Conclusion】Sublethal concentrations of EMB have significant impacts on the longevity and fecundity of S. furcifera adults, and can decrease the population size of their offspring. The results of this study provide a theoretical basis for the field control of S. furcifera in agriculture.

Key words:  Sogatella furcifera, emamectin benzoate, sublethal effect, age-stage, two-sex life table, fecundity