Sublethal effects of beta-cypermethrin on the bird cherry-oat aphid Rhopalosiphum padi (Hemiptera: Aphididae)

Rhopalosiphum padi is a sap-sucking aphid and an important pest of wheat that causes considerable yield loss. Beta-cypermethrin, a synthetic pyrethroid pesticide, has a broad insecticide spectrum and is considered effective for aphid control, while its residual concentrations may have sublethal effects on R. padi. Here, the sublethal effects of beta-cypermethrin on R. padi were conducted under laboratory conditions. The acute toxicity test showed that LC₁₀, LC₂₀, and LC₂₅ of beta-cypermethrin to R. padi adults were 0.003, 0.031 and 0.079 mg L^?1, respectively. The pre-adult survival rate was significantly reduced by all three concentrations. LC₂₀ significantly extended the development duration of 1st instar nymphs, pre-oviposition period, and oviposition period of R. padi. The adult longevity was also reduced by LC₂₅. However, the fecundity did not differ between the beta-cypermethrin treatment and control. For life table parameters, both the finite rate (λ) and intrinsic rate of increase (r) decreased at LC₁₀ and LC₂₀, as well as the net reproductive rate (R₀) reduced at LC₁₀ and LC₂₅, while mean generation time (T) increased at LC₂₀. Thus, at the concentrations of beta-cypermethrin tested here, there were negative impacts on R. padi fitness by decreased pre-adult survival rate, λ, r, and R₀, and delayed the development of some stages and increased T.