Contribution of host and environmental factors to the hyperparasitism of coffee rust under field conditions

Coffee rust is a devastating disease but its paratism by Lecanicillium lecanii is assumed as having little role in the disease progress. However, recent evidence showed that the ecology of the multitrophic interaction is more complex but the factors that contribute for Hemileia vastatrix parasitism have only started to be addressed. Surveys of rust and its parasitism in a coffee plantation where no fungicide was used were carried out to find out the contribution of the plant characteristics and environmental conditions on the dynamics of coffee rust and its parasitism by L. lecanii. Throughout the year, rust incidence/severity and hyperparasite presence were assessed monthly on leaves. The maximum parasitism was found in the dry season with high rates on the east-facing side of the plant rather than on the west-facing side. There was a positive correlation between hyperparasite incidence and rust incidence/severity, regardless of the plant parts or season and a stronger correlation in the upper part of the plant. H. vastatrix and L. lecanii were more frequently found at higher temperatures. The abiotic environmental factors as well as plant features play a strong role in epidemic rust and on its natural enemy. The results from this work showed that disease control strategies should take such factors and plant features into consideration in the integrated management of coffee rust, to rationally manage fungicide application and therefore both reduce production costs and the risk of the emergence of fungicide insensitive H. vastatrix populations.