TEMPORAL KYNAMICS OF PAPAYA RINGSPOT DISEASE

Epidemics of papaya ringspot disease (PRV)were monitored in fields in Guangzhou in 1988 and 1989.It was shown by analyzing the data of seasonal dynamics of disease develop-ment that the greatest rate of disease incidence increase appeared in early september.During the epidemic season, alate populations occurred in three peaks:early June,mid-August and mid-October.Ten to twenty days after each peak,there was a peak ofdisease incidence development.The seasonal dynamics of disease development and the growthand decline of the aphid populations were correlated to wind velocity,temperature and hu-midity.By comparing the fitness of three epidemic models (Logistic,Gompetz and Weibull)to the data of disease incidence,it was found that the disease development was best des-cribed by Gompertz model.With the equations of diseae progress,analyzing every parameterand calculating the number of days for disease to reach the incidence of 5%, 50%,90%,and99%,it was found that the disease epidemic pattern of papaya ringspotbelonged to the type of low virus source,low rate of infection and long epidemic pe-riod.By artificial inoculation with aphids(Myzus persicae),two models for infectiousand apparition dynamics of the disease were developped; both of them showed thatWeibull equation best described the dynamic of latent and incubation period,whichwere demonstrated to be about eleven and seventeen days respectively.