Abstract: To screen effective insecticides for controlling the mealybug（Phenacoccus solenopsis）from eggplant, the toxicity of mineral oil, thiamethoxam, and lambda-cyhalothrin against its 3rd instar nymphs was determined using the immersion method in the laboratory, and field efficacy validation trials were conducted. Laboratory toxicity results showed that all three insecticides exhibited toxic activity against both 3rd instar nymphs and female adults of P. solenopsis. Their LC₅₀ values were as follows: mineral oil（178.32 mg·L⁻¹ and 198.24 mg·L⁻¹）, thiamethoxam（8.76 mg·L⁻¹ and 11.24 mg·L⁻¹）, and lambda-cyhalothrin（25.41 mg·L⁻¹ and 22.70 mg·L⁻¹）. Thiamethoxam demonstrated the highest toxicity, superior to lambda-cyhalothrin and mineral oil. Field trial results on eggplant indicated that at recommended doses, 7 days after treatment（DAT）, mineral oil achieved the highest corrected control efficacy（77.8%）, followed by thiamethoxam（77.0%）, while lambda-cyhalothrin showed relatively lower efficacy（48.2%）. At 14 DAT, both thiamethoxam and mineral oil maintained high efficacy（＞90%）, whereas the efficacy of lambda-cyhalothrin declined significantly（to only 24.5%）. This study demonstrates that thiamethoxam and mineral oil are effective insecticides for controlling P. solenopsis, while lambda-cyhalothrin showed relatively poor efficacy and short persistence period.