FUNGICIDAL SELECTION PRESSURE ON MONILINIA VACCINII-CORYMBOSI (READE) HONEY IN WILD BLUEBERRY (VACCINIUM AUNGUSTIFOLIUM AITON)

Abstract

Propiconazole has been extensively used throughout the wild blueberry industry for Monilinia blight control over the past 20 years. Given the apparent loss of Monilinia blight control observed in field research trials and also in commercial fields, concerns were raised that the natural population of M. vaccinii-corymbosi (causal agent of Monilinia blight) was becoming less sensitive to propiconazole. Combined with this was uncertainty of the sensitivity of M. vaccinii-corymbosi to other fungicides. Thus, laboratory sensitivity analysis of M. vaccinii-corymbosi isolates to propiconazole, difenoconazole, prothioconazole-desthio, boscalid, penthiopyrad, and cyprodinil was completed. Field trials were set up to investigate Monilinia blight control efficacy of different fungicides. A significant shift toward reduced sensitivity to propiconazole in the population of M. vaccinii-corymbosi was not detected. Prothioconazole-desthio was the most effective active ingredient to inhibit mycelial growth of M. vaccinii-corymbosi. Consistently, Tilt® (a.i. propiconazole) and Proline® (a.i. prothioconazole) showed significant Monilinia blight control in vivo.