Tropical Plant Pathology (2018) 43, 533-542

Juliana S. Baggio, Nan-Yi Wang, Natalia A. Peres and Lilian Amorim (2018)
Baseline sensitivity of Colletotrichum acutatum isolates from Brazilian strawberry fields to azoxystrobin, difenoconazole, and thiophanate-methyl
Tropical Plant Pathology 43 (6), 533-542
Abstract: Anthracnose fruit rot, caused by Colletotrichum acutatum, is an important disease affecting strawberry fields in Brazil where fungicide applications are frequently needed for disease control. Isolates of C. acutatum were collected in conventional and organic strawberry fields in the states of São Paulo and Espírito Santo, Brazil, from 2013 to 2015. Sensitivity to azoxystrobin, difenoconazole and thiophanate-methyl was evaluated based on mycelial growth, spore germination, detached fruit assays and molecular characterization of genes targeted by these fungicides. The effective concentration needed to reduce mycelial growth by 50% (EC₅₀) was determined for 78 isolates. Mean EC₅₀ values for isolates collected in organic fields were 0.44 and 0.10 μg/ml, and in conventional areas were 0.62 and 0.09 μg/ml for azoxystrobin and difenoconazole, respectively. Mean EC₅₀ values, determined using spore germination test, for 43 isolates were 0.04 and 0.13 μg/ml for isolates from organic and conventional fields, respectively, for azoxystrobin. Azoxystrobin- and difenoconazole-resistant isolates were not observed. Populations of C. acutatum showed insensitivity rather than resistance to thiophanate-methyl and EC₅₀ values could not be determined. Molecular analyses of the cytb, cyp51 and β-tub genes did not reveal any of the most common point mutations associated with fungicide resistance.
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Database assignments for author(s): Natalia A. Peres, Lilian Amorim

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Colletotrichum acutatum	Strawberry (Fragaria)	Brazil (south)