Sensitivity to triadimefon of Rhizoctonia cerealis in Henan Province in 2017

In order to monitor the sensitivity of Rhizoctonia cerealis to triadimefon in Henan Province in China, the sensitivities of 169 isolates identified from 15 cities to triadimefon were determined by measuring the mycelial growth in the fungicide-amended media. The results showed that the EC₅₀ values of all isolates ranged from 0.82 to 12.62 μg/mL, and the sensitivity difference was 15.39 times. The average EC₅₀ value was (3.33 ± 1.91) μg/mL. The results of the frequency analysis showed that the EC₅₀ values of all 169 isolates to triadimefon was successively distributed, although EC₅₀ values of some isolates was beyond the sensitive baseline. 39.6% of the isolates (67 isolates) were concentrated in the main peak of the sensitivity frequency distribution, showing an approximate normal distribution. And the average EC₅₀ value of these isolate was (1.78 ± 0.44) μg/mL. The results obtained using the least significant difference method (LSD) and the cluster analysis both showed that there was no significant difference among the sensitivity of R. cerealis isolates to triadimefon in different areas, and there was no significant correlation between the sensitivity difference of R. cerealis isolates to triadimefon and the geographic location. Ratio and frequency of resistant isolates from different counties were not identical. Those results could direct the selection of fungicides used to control wheat sharp eyespot.