An analytical model of plant virus disease dynamics with roguing and replanting.
A mathematical model of the dynamics of a virus disease in a perennial plant population was developed. The population was divided into healthy, latently infected, infectious and post-infectious plants and the dynamics of each category was described by linked differential equations. Qualitative analysis of this model showed stable dynamics and threshold conditions for disease persistence. Stable equilibria were reached after several years. The dynamics of the model were highly sensitive to changes in contact rate and infectious period. Disease management by roguing (removal) of infected plants and replanting with healthy ones was investigated. Roguing only in the post-infectious category did not confer an advantage. At low contact rates, roguing only when plants became infectious was sufficient to eradicate the disease. At high contact rates, roguing both latently infected and infectious plants was advisable. With disease present, the equilibrium level of healthy plants did not depend on replanting rate, but at higher replanting rates the disease was more difficult to eradicate. There was a trade-off between roguing and replanting in designing opt. disease management strategies. Using parameter values estimated from field studies on 3 plant virus diseases, the model indicated that eradication was achievable with realistic roguing intensities.