Decoctos isolados e em mistura com fungicida no controle do oídio em minicepas de eucalipto

Abstract

The objective of the work was to evaluate the decoctions of Hyptis marrubioides, Aloysia gratissima and Cordia verbenacea and the mixture of those decoctions with the commercial fungicide pyra-clostrobin + epoxiconazole on the control of powdery mildew in eucalyptus. The experiment was conducted in a greenhouse using ministumps of Eucalyptus urophylla x E. camaldulensis (“urocam”) VM1 hybrid, consid-ered highly susceptible to powdery mildew. The treatments consisted of three decoctions at 50%, of the fungi-cide at 0,75 mL L-1 and the mixture of the decoction with the fungicide at the proportions of 50:50, 25:75 and 75:25, respectively. The treatments were sprayed every 14 days and the disease severity evaluations were car-ried out every 7 days. The direct fungitoxic effect of the treatments on the powdery mildew of the eucalyptus was evaluated by scanning electron microscopy (SEM). It was verified that the fungicide and decoctions of H.marrubioides, A. gratissima and C. verbenacea and all the mixtures of those decoctions with the fungicide were efficient in reducing the severity of powdery mildew in eucalyptus ministumps. The mixture of decoctions with the fungicide pyraclostrobin + epoxiconazole allowed us to reduce fungicide dose by 75% and increase the efficiency of control. Through the images obtained by SEM verified the fungitoxic action of the decoctions, the fungicide and combinations of these products on the powdery mildew of the eucalyptus, such as hyphal wall and conidiophore lysis and wilting of the fungal conidia.