Métodos de inoculação de Colletotrichum gloeosporioides e efeito de óleos essenciais no controle da antracnose em frutos de mamoeiro

Abstract

This study was composed by two experiments. The first experiment aimed to establish a simple and reliable method to inoculate Colletotrichum gloeosporioides on papaya fruits. The methods studied combined the maturation stage and two types of wounding to reproduce anthracnose symptoms in the laboratory. Papaya fruits in the 1 (with up to 15% of the yellowing skin), 2 (with up to 25% of the yellowing skin) and 3 (with up to 50% of the yellowing skin) maturation stages were wounded in two ways with needle number 6 and entomologic needle number 7 and then inoculated with a conidial suspension containing 2.5 x 106 conidia/mL of C. gloeosporioides. The fruits were kept in moist chamber during 48 hours, being stored at 23 to 27 °C. The evaluation of anthracnose symptoms was carried out 5 days after inoculation, where the diameter of the anthracnose lesions was measured. The maturation stages 2 and 3 associated with wound type 1 - five wounds made with a needle, showed to be efficient in the reproduction of anthracnose symptoms in laboratory conditions. In the second experiment the objective was to evaluate the effect of the essential oils of Syzygium aromaticum, Cymbopogon citratus and Thymus vulgaris using the fumigation and contact (immersion) methods on the micelial growth of C. gloeosporioides in vitro and in vivo. From the essential oils used in vitro, the most efficient in reducing the micelial growth by contact was the oil of S. aromaticum. By the fumigation treatment, except to C. citratus oil, in the lowest concentration, inhibited totally the growth of the fungus. In the in vivo test the essential oil of S. aromaticum showed to be promising for the control of the disease on the fruits by the immersion method.