Baseline sensitivity of Botrytis cinerea strawberry isolates from Brazil to fludioxonil and cyprodinil and disease control efficacy

Botrytis cinerea is an important pathogen in strawberry. The disease (gray mold) is difficult to control, causing losses in the field and during post-harvest. Chemical control is the most used method against this disease, but there are several reports of resistance to fungicides worldwide. The mixture of fungicides fludioxonil + cyprodinil was registered for strawberry in Brazil in 2019 but has not yet been widely used in the country. The objectives of this work were to determine the baseline sensitivity of B. cinerea isolates to fludioxonil and cyprodinil by in vitro assays and the efficacy of these fungicides in the control of post-harvest gray mold. In this study, the baseline sensitivity of B. cinerea isolates to fludioxonil and cyprodinil was established based on the EC50 of 100 isolates collected in the state of Parana in 2017. The EC50 value for fludioxonil ranged from 0.0028 to 0.0349 & mu;g/ml and EC50 values for cyprodinil ranged from 0.0035 to 77.17 & mu;g/ml. Four control efficacy trials were performed, with preventive and curative applications of detached strawberry fruit. The first experiment compared the control efficacy of fludioxonil to procymidone and fluazinam; the second and third compared cyprodinil to procymidone and fluazinam using sensitive and resistant isolates; and the fourth compared fludioxonil and cyprodinil with their mixture. Fludioxonil showed a control efficacy of 100% when applied preventively and 96.5% curatively, superior to procymidone and fluazinam; for cyprodinil, the highest efficacy was 85.7% in the preventive application. Fludioxonil and the mixture fludioxonil + cyprodinil had better efficacy preventively; however, curatively, fludioxonil was the most effective. These results indicate that the mixture of fludioxonil and cyprodinil fungicides is effective in controlling the disease, with fludioxonil being the most effective fungicide, both preventively and curatively. Thus, this fungicide mixture can be useful in the integrated management of gray mold of strawberry in Brazil.

Automated summary

Botrytis cinerea is a major pathogen in strawberry, causing significant losses both in the field and during post-harvest. Chemical control methods are commonly used, but resistance to fungicides has been reported worldwide. This study aimed to determine the baseline sensitivity of B. cinerea to fludioxonil and cyprodinil and evaluate the efficacy of these fungicides in controlling post-harvest gray mold.