The intensive use of benomyl in strawberry fields since the late 60s. resulted in an ineffective control of the flower blight, caused by Colletotrichum acutatum due to the development of resistance to the fungicide by the patogen, detected in 1984. Until recently, the resistance was not demonstrated in C. fragariae although an increasing failure of benomyl to provide satisfactory control of the crown rot ("chocolate" rot) has been observed, indicating the possible occurrence of resistance. To verify this evidence, 22 isolates of C. fragariae, collected at different localities in São Paulo State, were evaluated and compared with 22 isolates of C. acutatum. All the C. acutatum isolates were benomyl resistant, even at 1000 ppm. Among the 22 C. fragariae isolates, 10 were resitant. The percentages of mycelial growth inhibition of C. fragariae ranged from 50.0 to 88.8 (1 ppm), 54.5 to 89.8 (10 ppm), 63.6 to 78.7 (50 ppm), 67.3 to 80.3 (100 ppm), 74.4 to 82.0 (500 ppm) and 76.4 to 86.0 (1000 ppm). Resistant and sensitive isolates of C. fragariae were inoculated on strawberry plants of IAC-Campinas cultivar, causing similar symptoms.
strawberry; Fragaria X ananassa; anthracnose; fungicide; Benomyl; resistance; fungi