Effects of triflumezopyrim on the reproduction of brown planthopper, Nilaparvata lugens

The brown planthopper, Nilaparvata lugens Stål (Hemiptera: Delphacidae), is a notorious pest on rice in Asia and has evolved serious resistance to traditional chemical insecticides in recent years. Triflumezopyrim, a newly commercialized mesoionic insecticide, exhibited an excellent control effect on sucking insects, including N. lugens. However, the effects of triflumezopyrim on the reproduction of N. lugens have not yet been fully elucidated. In this study, we investigated the impacts of different concentrations of triflumezopyrim (LC₁₀, LC₅₀ and LC₉₀) on the reproduction and the reproduction related genes of N. lugens exposure to the insecticide via systemic and contact route. The results indicated that the preoviposition periods of N. lugens females in the LC₅₀ and LC₉₀ triflumezopyrim-treated groups (♀ t × ♂ t) were prolonged in contact toxicity treatment, compared with control (acetone treatment). The fecundities for three pair combinations (♀ c ×♂ t, ♀ t ×♂ c and ♀ t ×♂ t) treated with LC₅₀ and LC₉₀ concentrations of triflumezopyrim showed a significant decrease compared to water/acetone-treated control via contact and systemic route. No significant effects of LC₁₀ triflumezopyrim on preoviposition period and fecundity were found in contact and systemic toxicity treatments. However, the triflumezopyrim did not influence the egg hatchability. By microscope observation, the LC₅₀ and LC₉₀ triflumezopyrim impended the ovarian development in females. qRT-PCR analysis showed that the vitellogenin (NlVg) relative expression level of female adults exposed to LC₅₀ and LC₉₀ triflumezopyrim decreased by 30.3 – 39.5% in two toxicity treatments. The titers of another reproduction related hormones juvenile hormone III (JH III) in LC₅₀ and LC₉₀ triflumezopyrim-treatments were 27.4% and 25.8% lower than control in contact toxicity treatment and 27.08% and 37.18% lower than control in systemic toxicity treatment. In summary, these results suggested that the median lethal and high lethal concentrations of triflumezopyrim inhibited the reproduction and reduced the expression of NlVg and JH III in N. lugens. This study provided a reference for the efficient and scientific utilization of triflumezopyrim in the field.