Fungicide Sensitivity Assessed in Monilinia vaccinii-corymbosi Isolates from Lowbush Blueberry Fields in Maine

Abstract

The fungicide sensitivity in populations of Monilinia vacciniicorymbosi (Reade) Honey, the fungus that causes mummy berry, may be affected by the use of fungicides for control of this fungus. The sensitivity of M. vaccinii-corymbosi isolates from conventionally and organically managed fields and an unmanaged, wild area was determined for the fungicides propiconazole and fenbuconazole. Propiconazole has been used for more than 14 years to control mummy berry, and fenbuconazole has become more widely used in the last 4 years than previously. The baseline EC50 for isolates from the unmanaged area was significantly higher for propiconazole (0.016 μg/ml) than fenbuconazole (0.006 μg/ml). The propiconazole EC50 for isolates from conventionally managed fields (0.020 μg/ml) was significantly higher than for isolates from the unmanaged area (0.016 μg/ml), but not from the organically managed fields (0.018 μg/ml). No significant differences in the fenbuconazole EC50 were found among management types. The biennial long-term use of the fungicide propiconazole on populations of M. vaccinii-corymbosi may contribute to the development of fungicide insensitivity over time. Accepted 15 August 2014. Published 24 September 2014.