Abstract: To research the effect mechanism on ecological control of population of the brown planthopper (BPH), Nilaparvata lugens (Stål), the control effect of secondary metabolities against BPH was simulated and evaluated using state space equation and factor-adding analysis method. The different combining of alcohol extracts from Mikania micrantha, Eupatorium odoratum and Melia azedarach employed BPH population, and constructed the control model of Nilaparvata lugens population system. Based on the data from different stages, the values of systematic matrix were fitted, and the control effect of secondary metabolities against BPH was simulated. The results showed that the secondary metabolites of Mikania micrantha, Eupatorium odoratum, Melia azedarach applied alone, could drastically decrease the population quantity of BPH, yet the population trend index (I) was still above 1.00, which could not control BPH population to a sustainable decrease. Either two or three kinds of secondary metabolites simultaneously could control the increase of BPH population effectively. Meanwhile, the control mechanism of secondary metabolites on BPH population was its deterrent effect, especially in the initial stages of population development. The egg number of BPH was reduced significantly due to the strong deterrent effect on adults of BPH. As a result, the population number and the harm of BPH population were reduced significantly.

Key words: Brown planthopper (Nilaparvata lugens), secondary metabolites, factor-adding analysis method, simulation, Mikania micrantha, Eupatorium odoratum, Melia azedarach, alcohol extract