Sensitivity of Colletotrichum acutatum isolates obtained from strawberry to tiophanate-methyl and azoxystrobin fungicides

Abstract

The objective of this study was to determine the sensitivity of Colletotrichum acutatum to the fungicides thiophanate-methyl and azoxystrobin, based on mycelial growth and conidia germination. Sixty monoconidial isolates from two strawberry-producing regions of Michoacan state were evaluated in culture medium amended with fungicides at 0.001, 0.01, 0.1, 1 and 10, 100 and 2000 μg mL-1. The effective dose that reduced mycelial growth by 50 % (ED50) of thiophanatemethyl varied from 0.28 to 9.72 μg mL-1 in the Maravatío Valley and from 1.39 to 2.99 μg mL-1 in the Zamora Valley. In conidia, the ED50 ranged from 0.9 to 396.4 μg mL-1 in the Maravatío Valley and from 0.43 to 63.32 μg mL-1 in the Zamora Valley. For azoxystrobin the ED50 in mycelium ranged from 0.04 to 0.36 μg mL-1 in Maravatío and from 0.07 to 0.99 μg mL-1 in Zamora. In the conidia the ED50 varied from 0.01 to 0.56 μg mL-1 for Maravatío and 0.006 to 0.15 μg mL-1 in Zamora. The ED50 distributions indicated that C. acutatum isolates were sensitive to azoxystrobin and moderately resistant to methyl thiophanate.