Susceptibility to Botrytis blight at different floral stages of wild blueberry phenotypes

Botrytis blossom blight is an important disease of wild blueberries with yield losses in excess of 20% frequently occurring. Two field experiments were conducted in 2016 and 2017 to determine the susceptibility of four phenotypes (Vaccinium angustifolium, V. angustifolium f. nigrum, V. myrtilloides and V. angustifolium var. Fundy] at different floral stages [(Bud break (F5); bud prebloom; (F6), corolla fully open (F7), and senescent corolla (F8)] to Botrytis infection. Specific flower clusters on tagged stems from different phenotypes were inoculated with Botrytis cinerea conidial suspension (10⁶ conidia·ml^-1). Disease development were assessed eight days after inoculation. Disease incidence and severity in phenotype ranged from 14.1 to 22.6% and 37.4 to 42.3% in 2016, respectively, and 39.8 to 44.1% and 9.70 to 19.1% in 2017, respectively. Results indicated that V. angustifolium was the most susceptible followed by V. angustifolium f. nigrum and V. angustifolium var. Fundy. Vaccinium myrtilloides was found to be least susceptible. Incidence and severity on floral stages ranged from 2.95 to 36.4% and 7.81 to 75.5% in 2016, respectively, and 7.28 to 66.9% and 11.1 to 27.1% in 2017, respectively. Floral stage F7 was the most susceptible with incidence up to 66.9% and severity up to 75.5% followed by F6, F5 and F8. Therefore, results from this study indicated that V. myrtilloides was less susceptible to B. cinerea than V. angustifolium phenotypes, and F6 and F7 stages were the most susceptible to Botrytis blight. These results will assist producers in making more informed decisions on Botrytis blight control and as its management practices shift from blanket to precise delivery of disease control products.