Incidência de doenças foliares em sistemas de policultivo: Mixed cropping systems can be an alternative to traditional cultivation methods in humid tropical areas such as Amazonia. The dispersion of species in the cultivated area will probably reduce the incidence of disease, because the non-host plants serve as a barrier to the spread of pathogens. Recultivation of abandoned area with the aid of mixed cropping systems has been studied. Since July 1993, the severity of infection of rubber trees has been assessed weekly and the incidence of disease in the other crops monitored monthly. Only rubber, orange, cassava and papaya have been affected. As the plants have not yet reached asufficient height to form pathogen barriers, the differences between the monocultures and the mixed cultivation systems are not significant.The occurrence of Microcyclus ulei and Thanatephorus cucumeris in rubber, Phytophthora citrophthora, Septobasidium pseudopediculatum and S. sacardium in orange. Meloidogyne sp. in papaya and Xanthomonas campestris p.v. manihotis in cassava are discussed
