An epidemiological model of the corn stunt system in Central America

Abstract

There is increasing appreciation on the part of ecologists of the crucial role that pathogens may play in the structure of plant populations and communities. This study used classic equations of epidemiology to analyze corn stunt in Central America, which includes a leafhopper, Dalbulus maidis, a spiroplasma, and corn, Zea mays. Given the underlying structure, the system is expected always to tend to a 100% infection rate of the corn. The prospect of artificially raising the death rate of infected corn, that is, the selective destruction of infected corn plants or highly infected fields, was investigated using this model. The destruction of infected plants must be greater as the transmission probabilities increase, as the disappearance rate of the leafhopper decreases, and as the number of leafhoppers per plant decreases. Parameters of the model were estimated using data from Nicaragua and Costa Rica. To control the disease by eliminating infected corn plants would require elimination of between 0.11% and 8.3% of the population per week in Nicaragua; the corresponding figures for Costa Rica were 2.2% to > 100%.