Modelling the dynamics of Pine Wilt Disease with asymptomatic carriers and optimal control

Muhammad Altaf Khan,Mainul Haque,L Ahmed,Prashanta Kumar Mandal,Robert Smith

doi:10.1038/s41598-020-67090-7

Muhammad Altaf Khan, Mainul Haque + Show 3 more

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https://doi.org/10.1038/s41598-020-67090-7

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Pine wilt disease is a lethal tree disease caused by nematodes carried by pine sawyer beetles. Once affected, the trees are destroyed within a few months, resulting in significant environmental and economic losses. The role of asymptomatic carrier trees in the disease dynamics remains unclear. We developed a mathematical model to investigate the effect of asymptomatic carriers on the long-term outcome of the disease. We performed a stability and sensitivity analysis to identify key parameters and used optimal control to examine several intervention options. Our model shows that, with the application of suitable controls, the disease can be eliminated in the vector population and all tree populations except for asymptomatic carriers. Of the possible controls (tree injection, elimination of infected trees, insecticide spraying), we determined that elimination of infected trees is crucial. However, if the costs of insecticide spraying increase, it can be supplemented (although not replaced entirely) by tree injection, so long as some spraying is still undertaken.

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Among the vector-borne diseases of trees and plants, the most destructive are a red ring disease of palms and Pine Wilt Disease (PWD), whose causative agent is pine wood nematodes (PWNs)[1]
We considered two controls: the elimination of infected trees (u2) and the spraying of insecticides (u3) in the absence of tree injection and vaccination
We see a rapid increase in the population of susceptible trees (Fig. 3(a)) and eventual elimination of exposed and infected trees (Fig. 3(b,d)), with only the asymptomatic carriers remaining in the infected classes (Fig. 3(c))

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Introduction

Among the vector-borne diseases of trees and plants, the most destructive are a red ring disease of palms and Pine Wilt Disease (PWD), whose causative agent is pine wood nematodes (PWNs)[1]. 0 is most sensitive to γ1 and γ2, the natural death rates of pine trees and beetles, respectively; the latter can be controlled using insecticide (u3), while the former can be partially controlled by eliminating infected trees (u2).

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