An agent-based model of Eldana Saccharina Walker

[摘要] ENGLISH ABSTRACT: An agent-based simulation model is formulated in this dissertation in order to simulate the population dynamics of Eldana saccharina Walker infestation in sugarcane. The simulation modelcomprises four distinct building blocks, namely a graphical user interface, the implementationof the life cycle and associated influence of temperature on E. saccharina, the mating processof E. saccharina and the oviposition and dispersal of E. saccharina. These building blocks arebased on existing literature pertaining to the biology and behaviour of the pest and, in caseswhere the relevant literature is insu cient or non-existent, expert opinion and careful assumption.In order to select areas from existing sugarcane farms on which to execute location-speci cexperiments, functionality which allows Geographic Information Systems (GIS) data importationis included as a platform on which to run the simulation model. These data inform themodel in respect of the shape and characteristics of the underlying sugarcaneelds in which thesimulated E. saccharina population interacts.The model interacts and operates within an AnyLogic simulation software environment and, inso doing, aims to emulate the behaviour of a population of E. saccharina moths in sugarcane. It isanticipated that the model implementation may serve as a basis for facilitating future design andtesting of control measures in order to suppress the pest and its consequent detrimental e ectto sugarcane through infestation and feeding on interior stalk nutrients. Numerous workingmathematical models of the pest exist in the literature, but, in all previous cases, intricateaspects of the stalk borer's biology have been aggregated on a population level and averagepopulation changes have been a ected at discrete time steps. The resulting analyses thereforeyield conclusions that do not necessarily reect the continuous, changing nature of E. saccharinaon a localised level. Using agent-based modelling, however, the pest's behaviour may be modelledin more detail so as to facilitate more thorough investigation of potential control strategies andtheir expected e cacy on the pest at di erent points in its life cycle.The agent-based simulation model designed in this dissertation is subjected to a number ofveri cation and validation techniques. Furthermore, a pilot sensitivity analysis is conducted toidentify the most inuential parameters in the simulation model. These parameters are thenconsidered further in a comprehensive parameter variation analysis in order to illustrate theexibility and diversity of the model in terms of the variety of scenarios pertaining to E. saccha-rina population behaviour that it can accommodate. In some cases, simpli ed implementationsof control measures are also imposed on the pest within the model in order to further illustrateits implementation capabilities, as anticipated for future model development and use.In light of this exibility, the model is also presented as a computerised decision support andanalysis tool, including the ability to upload and recreate a speci c user's own sugarcane farmshape le, as well as to alter a set of available parameters. This may aid in simulating speci cbehaviour in a simulation run in accordance with what has typically been observed by theuser, or of hypothetical scenarios which require investigation. In turn, as the model is furtherdeveloped and detailed control measures are included as part of the simulation execution, it isbelieved that an appropriate response pertinent to the characteristics of the geographical areaunder consideration and the corresponding E. saccharina population present in this area may bepredicted, allowing for control measure alteration and redesign so as to optimise the associatedparameters or actions prior to in- eld implementation.In order to further re ne the model and improve its accuracy, as well as ensure agreementbetween the existing modelling approaches and actual biological processes in nature, the entiresimulation model of E. saccharina is subjected to an expert panel discussion. The expertscomprising the panel encompass some of the key researchers pertaining to E. saccharina andother moth behaviour and population dynamics, both in South Africa and internationally. Thesimulation model is updated or adjusted according to suggestions made and new informationshared by the expert panel in an attempt to simulate the pest as accurately as possible inaccordance with the body of knowledge currently available.Although several other approaches to modelling E. saccharina populations have been adoptedin the past, no existing models implement such a low level of abstraction with respect to thebiology of the pest. In addition, previous models are often case-speci c, investigating speci ccontrol measures that are imposed on an aggregate level on a population of the pest. By activelysimulating E. saccharina's biological decision-making processes, intricate aspects pertaining toone or a number of interacting control strategies, as well as the manner in which they alterthe pest's biology or behaviour, may easily be incorporated using an agent-based simulationmodelling approach. Adopting a low level of abstraction also requires extensive informationpertaining to the pest and, as such, areas where little understanding still exists with respectto the behaviour of E. saccharina have been highlighted and, consequently, may be prioritisedfor future entomological research by experts in theeld. Finally, numerous options for futureinvestigation into this problem, including model re nement, control measure design and testingand comparison to existing models, pose positive possibilities for the eventual establishment ofa functional, integrated pest management programme for E. saccharina.

[发布机构] Stellenbosch University