Avaliação da sensibilidade micelial a fungicidas de Colletotrichum spp. associadas à atemoia no Estado de Alagoas

Abstract

Anthracnose, caused by Colletotrichum spp., is an important disease of atemoya causing damage in different organs of the plant, highlighting those caused in the fruit, both pre- and post-harvest. The symptoms of this disease range from leaf anthracnose, flower abortion, branch tip burn, and necrotic lesions on the fruit. Knowing the action of certain fungicides to combat the etiologic agent is essential to develop control techniques. Given this, the present work aimed to evaluate the mycelial sensitivity of Colletotrichum species, from atemoya to the fungicides thiophanate methyl, azoxystrobin and tebuconazole. To determine the sensitivity of Colletotrichum species to fungicides, mycelial growth was evaluated on synthetic potato-dextrose-agar (PDA) medium supplemented with fungicide. The fungicides were dissolved in dimethyl sulfoxide (DMSO) and added to the melting synthetic culture medium (45°C) to reach the concentrations of 0.0, 0.1, 0.5, 1.0, 5.0 and 10 μg/ml-1 i.a. Daily, the mycelial growth of each colony was measured in two perpendicular directions to obtain the mycelial growth index (MCI). The EC50, the active ingredient concentration capable of inhibiting 50% of mycelial growth, was also calculated. After calculating the EC50, Colletotrichum species were classified into three sensitivity categories where: EC50: <10 μg/ml-1 : high sensitivity (AS); EC50: 10-100 μg/ml-1 : moderate sensitivity (MS); EC50: 100-500 μg/ml-1 : insensitivity (I). The species C. theobromicola, C. fruticola, C. siamense and C. karstii were highly sensitive to the fungicides tebuconazole and thiophanate methyl. The fungicide azoxystrobin was efficient in controlling C. theobromicola in vitro, but was inefficient in controlling C. siamense. The species C. fruticola and C. karstii were moderately sensitive to the fungicide azoxystrobin.