Potential effects of air pollutants on epidemics of plant diseases

Abstract

Air pollutants potentially can affect plant disease epidemics in numerous ways. The initial disease level ( y 0) and the apparent infection rate ( r, a parameter measuring the rate of disease increase) can be altered by pollutants. For compound interest diseases, final disease intensity is more sensitive to changes in r than to y o . The effective multiplication factor ( R), the latent ( p) and infectious ( i) periods determine r. These values, however, are not equally important in affecting r. One can use fairly simple equations to relate constant values of R, p, and i to r during the early stages of an epidemic. Nonconstancy of these characteristics, due either to changing environment or inherent variability of the population, generally requires computer simulation for a thorough understanding. Spatial variability and pathogen dispersal further complicate the effect of pollutants on plant disease epidemics. Some reported examples of the effects of 03, SO, and acid deposition on epidemic characteristics are discussed.