Abstract: 【Aim】 This study aims to explore the effects of beta-cypermethrin (β-cypermethrin) on the biological characteristics of Carposina sasakii Matsumura, especially the sublethal effects of beta-cypermethrin on the development, survivorship and reproduction of the F₀ (parental) and F₁ generations of C. sasakii. 【Methods】 The sublethal concentrations (LC₁₀, LC₂₀ and LC₄₀) of β-cypermethrin against the newly hatched larvae of C. sasakii were determined by fruitdipping method. The mortality of C. sasakii was recorded at 24 h after treatment and the LC₁₀, LC₂₀ and LC₄₀ values were estimated using DPS software. Sublethal effects of β-cypermethrin on the development and reproduction of the F₀ and F₁ generations were assessed by establishing a life table. The statistical differences of the survivorship and developmental duration, the adult longevity, the number of eggs laid per female and life table parameters of F₀ and F₁ generations were analyzed with SPSS 21.0. 【Results】 According to the bioassay results, the LC₁₀, LC₂₀ and LC₄₀ values of β-cypermethrin on the newly hatched larvae of C. sasakii at 24 h after treatment were 0.146, 0.267 and 0.579 mg/L, respectively. Sublethal concentrations of β-cypermethrin reduced the survivorship and the proportion of female adults of F₀ and F₁ generations. The values of boring rate, exiting rate, and survival rate of larvae, emergence rate and sex ratio (♀/♂) reduced with the increase of the insecticide concentration. After the newly hatched larvae of F₀ generation were exposed to the sublethal concentrations (LC₁₀, LC₂₀ and LC₄₀) of β-cypermethrin, the average numbers of eggs laid per female per day were 34.09, 33.00 and 30.12, respectively; correspondingly, the numbers of eggs laid per female were 284.90, 276.56 and 252.89, respectively, both were significantly less than those of the control (38.02 and 320.98, respectively). When the newly hatched larvae of F₁ generation were exposed to LC₁₀, LC₂₀ and LC₄₀ of β-cypermethrin, the average numbers of eggs laid per female per day were 34.57, 30.82 and 33.39, respectively, which were significantly higher than that of the control (27.97). Meanwhile, the numbers of eggs laid per female after treatment with β-cypermethrin at LC₂₀ and LC₄₀ were 304.45 and 298.31, respectively, which were significantly higher than that of the control (271.40). However, there was no significant difference in the developmental duration of each stage and the larval weight as compared with the control. Life table analysis showed that the net reproductive rate (R₀) decreased significantly in a dose-dependent manner after treatment. The R₀ values of the F₀ generation decreased significantly after treatment with β-cypermethrin at LC₁₀, LC₂₀ and LC₄₀ with the values of 124.36, 114.33 and 60.16, respectively, as compared with the control (166.54), while the corresponding values of the F₁ generation were 128.84, 112.30 and 85.32, respectively, as compared with the control (128.80). Sublethal concentrations of β-cypermethrin obviously reduced the relative fitness value (R_f) of the F₀ and F₁ generations. The R_f values of the F₀ generation after treatment with β-cypermethrin at LC₁₀, LC₂₀ and LC₄₀ were only 0.75-, 0.68- and 0.37-fold as high as that of the control, while those of the F₁ generation increased to 0.98-, 0.86- and 0.64-fold as high as that of the control. 【Conclusion】 Sublethal concentrations of β-cypermethrin influence the survivorship, growth and reproduction of F₀ and F₁ generations of C. sasakii, consequently affecting its population dynamics. β-cypermethrin applied singly or sequentially would inhibit the population growth rate of C. sasakii, but its reproductive disadvantage would be improved after a secondary or more treatments.

Key words: Carposina sasakii, beta-cypermethrin, sublethal concentration, biological characteristics, life table, relative fitness