Sensibilidade de espécies de Colletotrichum a fungicidas e influência de períodos de permanência em câmara úmida sobre a severidade da antracnose em anonáceas

Abstract

Anonáceas have great economic importance in Brazil and in the world, among the main species is the pine (Annona squamosa L.) and graviola (Annona muricata L.). These fruits are subject to several types of diseases, the main one being the anthracnose, which has as causal agent, species of the genus Colletotrichum, causing significant losses of up to 70% of the production. The objective of this work was to evaluate the in vitro sensitivity of five species of Colletotrichum to five fungicides of different actives principles and the mixtures of azoxystrobin + difenoconazole and azoxystrobin + SHAM, as well as to evaluate the spore germination of Colletotrichum species and also the influence of periods of wet camera stay on the severity of anthracnose in pineapple and graviola. Isolates from Colletotrichum species were grown in synthetic BDA medium containing the fungicides (azoxystrobin difenoconazole, tebuconazole, methyl thiophanate, copper oxychloride and azoxystrobin + difenoconazole) in the following 0,0 concentrations; 0,1; 0,5; 1; 5 and 10 μg of i.a. ml-1 and azoxystrobin (10mg / ml-1) + SHAM, incubated in BOD at 25 °C in the dark. The evaluations were carried out for seven days by measuring mycelial growth. The inhibition test of conidia germination was carried out with the dilution of fungicides in sterile distilled water (ADE), obtaining concentrations of 0,1; 0,5; 1; 5; 10 μg ml-1 of the fungicides and conidial concentration of 2x106 ml-1. Two periods of stay in humid chamber (2 and 5 days) were used in pines and soursop leaves, at temperatures of 20, 25 and 30 oC. According to the results, it was possible to observe that the fungicides difenoconazole, tebuconazole, methyl thiophanate and azoxystrobin + difenoconazole showed better performance in the in vitro control with ED50 values between 0,1 and 0,75 mg / ml and inhibition of conidial germination of Colletotrichum species, copper oxychloride was not satisfactorily controlled. . The fungicide azoxystrobin associated with salicylhydroxamic acid (SHAM) totally inhibited the mycelial growth of Colletotrichum species. The temperature of 25ºC and the period of stay of 5 days favored the appearance of anthracnose symptoms in leaves of pineapple (Annona squamosa L.) and graviola (Annona muricata L).