Research On The Integrated Management Ecosystem Of Several Types Of Mixed Pests

The accurate description of the integrated pest management is "by using the worms,birds and bacterium to fight against the insects" which fully embodies,in the process of pest control,the importance of how to maintain the balance of ecosystem(the Volterra principle by using the worms and birds to fight against the insects)and the application of biological pesticides(using the bacteria to fight against the insects).It is well known that chemical pesticides are usually treated as the main strategy of pest control because of their durability,high efficiency,convenient application and so on.However,the high-frequency and high-dose use of pesticides not only will cause serious environmental problems,but also will lead to the second resurgence of pests or being rampant owing to the development of pest resistance to drugs and the decline of pesticide effects.Therefore,it can be seen that the integrated pest management is a complex system,which requires to synthetically take into account the interaction between pests and natural enemies,the correlation of numerous control strategies,including the chemical control and biological control,the relationship between the strategy implementation and the development of pest resistance.These comprehensive fac-tors play an important role in the success or failure of integrated pest management,which needs to be analyzed and studied systematically by means of mathematical model,theoretical analysis and computer implementation and so on.At present,a number of mathematical models are designed to consider a single control factor,and develop a relatively simple mathematical model to analyze the effectiveness of the control strategy,which completely ignores the influences of the comprehensive factors,including " using the worms,birds and bacterium to fight against the insects" and the development of insect resistance on pest control and so on.Therefore,according to the inherent law of pest population growth and the implementation of control strategies with different schemes as well as the considering of the comprehen-sive control strategy,including biological insecticide,the dynamic evolution of pest resistance and the control strategy on different time intervals and so on,we develop the novel mathematical model,the analytic technique and numerical method,and systematically analyze the complex ecological system with integrated pest manage-ment strategy,then explore the optimal control strategy for different implementation schemes.At the same time,the proposal of the different management measures for the development of pest resistance and the study of the control strategy on different time intervals bring in a great challenge on the numerical analysis.In the second chapter,under the consideration of introducing pathogenic mi-croorganism as biological pesticide to make the pest population possess the ability to spread diseases as well as different control strategies,such as spraying pesticides,the releases of infected prey and natural enemies,we propose a pest-natural enemy ecosystem with multiple pulse control measures at fixed time to study how do the spread of diseases among pests,pesticide spraying and the releases of infected pests and natural enemies with different frequencies impact the threshold condition about the stability of the pest eradicated periodic solution,and further seek the best fre-quency or the best spraying period for the implementation of pesticide spraying,and then according to the "Volterra" principle,we discuss the best quantity of pesticide application,all of which help to obtain the best pest control scheme.If the frequency of pesticide application is lower than that of infected pest releases,then there exists an optimal release quantity of the natural enemies to minimize the threshold;The numerical simulations show that when choosing different parameter spaces,the two attractors of the system coexist within a large range of parameters,that is,there exist different erupted densities of pest population under different initial conditions,so the design of pest control strategy needs to closely monitor the initial dynamics of pests.In the third chapter,based on the influence of the economic threshold level of pest control and the frequency of pesticide implementation on the development of pest resistance,firstly,a growth model of pest population with state-dependent feedback is established to depict the interaction between population growth and pest resistance.Moreover,it follows from the requirement of actual control and theoret-ical derivation that four switching strategies of resistance management,including the threshold level-guided,the time interval-guided,the resistance ratio-guided and the period-guided are proposed.Then,we build and develop a pest-natural en-emy ecosystem with state-dependent and the dynamic evolution of pest resistance,and then it follows from the period-guided switching strategy that we systemically investigate different dynamic behaviors of the model,including the definition of pe-riodic Poincare mapping and its properties,the existence and stability of the pest eradicated periodic solution,the existence and stability of fixed points for Poincare mappings as well as the existence and stability of various periodic solutions.In par-ticular,the existence and stability of the periodic solutions of the system,as well as the maximum number of pesticide spraying and the switching period of pesticides provide important ideas for how to manage the development of resistance and the best handover strategy.In the fourth chapter,a discrete host-parasitic ecosystem with integrated pest management strategy is firstly proposed based on the pest population with non-overlapping generation,then it follows from the management target guided by the economic threshold level that the model is developed as a discrete switched system with the use of control strategies on different time intervals.By the development of numerical analysis techniques,we focus on the existence and stability of several types of equilibria of the switched system,and identify different parameter regions for the existence of the real and virtual equilibria,which plays an important role in the selection of parameter regions so that the density of pest population can stabilize in the free subsystem.Furthermore,based on the phenomenon of multiple attractor coexistence,the influence of non-constant death rate and release amount with random disturbances on the dynamic behaviors of discrete switched systems is analyzed.We focus on how do the key parameters and initial densities of the host and parasitic populations affect the outbreak of host,the switching frequency or the average switching frequency,and the main results reveal what the key factors affect the switching among attractors,all of which provide an idea to optimize the pest control strategy.