Analysisofpesticideefficiencyofinsecticidesagainstbrownplanthopper,<italic>Nilaparvatalugens</italic>Stål

According to the reported data, such as the toxicity of pesticide against the brown planthoppe, Nilaparvata lugens Stål, the field distribution of pesticides after leaf spraying and etc., it was found that the effective utilization rate of insecticides for controlling N. lugens was less than 0.1%. LD₉₀ (μg/pest), which was determined by indoor bioassay, was the lethal dose of the insecticides which can kill 90% population of N. lugens. Theoretically, the amount of N. lugens in paddy field multiply by LD₉₀ was the dosage to kill 90% population of the pest. However, the recommended dosage of insecticides was 1000 times higher than the theoretical effective dosage. There were three reasons for this phenomenon. First, during the booting stage and flowering stage of rice, which were the harmful period of N. lugens, the deposition rate of insecticide on rice plant sprayed by manual sprayer was 34.25%-46.10%, of which more than 82% was distributed at the rice canopy and less than 2% at the rice stem stalk below the canopy. Overall, only about 0.5% of the insecticide dosage deposited on the rice stem. Second, the N. lugens was killed after treated by a lethal dose. However, the distribution of insecticide and N. lugens was extremely uneven in paddy field. When the lowest dose of insecticide and the largest number of N. lugens were on the same rice plant, the dose of insecticide should still be enough to control N. lugens. Therefore, the dose of insecticide was wasted when the more insecticide doses was deposited on the location with less brown planthopper. Thus, the effective utilization rate of pesticides was further reduced. Third, more than 50% of pesticide dosage dropped in paddy field water and diluted by the water. The concentration of the pesticide was less than the lethal concentration of the insecticides that can kill 10% population of N. lugens (LC₁₀), which could not effectively control N. lugens. Through artificial intelligence, the insecticide was sprayed directly on the site where the N. lugen was harmful, and the insecticide was applied in variable according to the amount of the insect, which will greatly improve the effective utilization rate of the insecticide in the control of N. lugen.