Sensitivity of Brazilian Botrytis cinerea isolates from strawberry to pyrimethanil and its control efficacy

Due to the significant losses caused by the pathogen Botrytis cinerea in strawberry, the use of effective management is highly needed but can be difficult to achieve. Chemical control is the main method used against B. cinerea, but the pathogen has shown resistance to several fungicides worldwide. The fungicide pyrimethanil is registered for strawberry in Brazil, but it is still not widely used by growers in Parana state. The objectives of this study were to evaluate the sensitivity of B. cinerea isolates to pyrimethanil, to verify possible cross-resistance between pyrimethanil and cyprodinil, and to evaluate the efficacy of pyrimethanil in controlling gray mold. The sensitivity of B. cinerea isolates to pyrimethanil was established based on the EC50 of 100 isolates collected in the state of Parana in 2017. EC50 values of B. cinerea for pyrimethanil ranged from 0.0052 to 94.07 & mu;g/ml with a mean EC50 value of 6.53 & PLUSMN; 15.17 & mu;g/ml. There was a positive correlation between pyrimethanil and cyprodinil EC50 values (r = 0.83). The efficacy of preventive and curative applications of pyrimethanil, cyprodinil and fludioxonil was evaluated in detached strawberry fruit assays with sensitive and resistant isolates to pyrimethanil. Fludioxonil was the most effective in controlling the disease both isolates and application types. Pyrimethanil and cyprodinil showed greater efficacy when applied using sensitive isolate preventively, with control efficacy of 84.61 and 87.17%, respectively. Overall, pyrimethanil showed good efficacy in the control of gray mold of strawberry and can be recommended for managing the disease, but its use requires monitoring to avoid the selection of resistant isolates in the short term.

Automated summary

Due to the significant losses caused by the pathogen Botrytis cinerea in strawberry, effective management is needed but can be difficult to achieve due to the pathogen's resistance to fungicides. This study evaluated the sensitivity of B. cinerea isolates to the fungicide pyrimethanil and found a positive correlation between pyrimethanil and cyprodinil resistance. Pyrimethanil showed good efficacy in controlling gray mold of strawberry, but monitoring is necessary to prevent the selection of resistant isolates.