AN ANALYTICAL MODEL OF PLANT-VIRUS DISEASE DYNAMICS WITH ROGUING AND REPLANTING

1. The dynamics of a virus disease in a perennial plant population are modelled. The population is divided into healthy, latently infected, infectious and post-infectious plants and linked differential equations describe the dynamics of each category. 2. Qualitative analysis of this model shows stable dynamics and threshold conditions for disease persistence. Stable equilibria are reached after several years. The dynamics of the model are highly sensitive to changes in contact rate and infectious period. 3. Disease management by roguing (removal) of infected plants and replanting with healthy ones is investigated, Roguing only in the post-infectious category confers no advantage. At low contact rates, roguing only when plants become infectious is sufficient to eradicate the disease. At high contact rates, roguing latently infected as well as infectious plants is advisable. 4. With disease present the equilibrium level of healthy plants does not depend on replanting rate, but at higher replanting rates the disease is more difficult to eradicate. There is a trade-off between roguing and replanting in designing optimal disease management strategies. 5. Using parameter values estimated from field studies on three plant virus diseases, the model indicates that eradication is achievable with realistic roguing intensities.