To clarify the effects of the median lethal concentrations（LC₅₀） of lambda-cyhalothrin and thiamethoxam on the growth， development and reproduction of Frankliniella intonsa resistant populations in alfalfa fields， two field-resistant populations （YLC and MS） from Ningxia were used as test materials. Stress treatments were conducted based on laboratory toxicity assays， and the effects of the two insecticides on the fecundity， developmental duration， body length， body width， adult longevity and survival rate of the offspring of Frankliniella intonsa were investigated. The results showed that under the stress of median lethal concentration of the two insecticides， the fecundity of F₁ adults decreased significantly； the developmental duration of F₂ eggs and first-instar nymphs was significantly prolonged； the body length and body width of F₂ first-and second-instar nymphs were significantly reduced； the longevity of F₂ adults was significantly shortened； and the survival rate of F₂ at each developmental stage was significantly decreased. This study confirmed that the median lethal concentration of lambda-cyhalothrin and thiamethoxam could significantly inhibit the reproduction， growth， development and survival of Frankliniella intonsa populations， providing important technical support for the scientific management of field insect pests.

Frankliniella intonsa  /  Median lethal concentration  /  insecticide  /  growth and development  /  insecticide resistance