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 both pre and post-harvest. Symptoms of this disease range from foliar anthracnose, flower abortion, branch blight and necrotic fruit lesions. Knowing the action of certain fungicides in the fight against the etiological agent is essential to develop control techniques. The objective of this work was to evaluate the mycelial sensitivity of Colletotrichum spp., from atemoya, to the fungicides thiophanate methyl, azoxystrobin and tebuconazole. To determine the sensitivity of Colletotrichum species to fungicides, mycelial growth in synthetic potato-dextrose-agar (PDA) supplemented with fungicide was evaluated. The fungicides were dissolved in dimethylsulfoxide (DMSO) and added to the fluxing culture medium (45°C), to reach concentrations of 0.0, 0.1, 0.5, 1.0, 5.0 and 10 μg/ml-1 of a.i. The mycelial growth of each colony was measured daily to obtain the mycelial growth index (ICM). EC50 was also calculated. After calculating the EC50, the Colletotrichum species were classified into three sensitivity categories, where: EC50: <10 μg/ml-1: high sensitivity (SA); 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 proved to be efficient in the in vitro control of the species C. theobromicola, however, it proved to be inefficient for the control of the species C. siamense. The species C. fruticola and C. karstii were moderately sensitive to the fungicide azoxystrobin.