Susceptibility of Southern Blueberry Cultivars to BotrytisBlossom Blight

Abstract

The susceptibility of blueberry flowers at various developmental stages was evaluated by inoculating potted blueberry bushes of the rabbiteye cultivars, Climax, Premier and Tifblue, and the southern highbush cultivars, Magnolia and Jubilee, during bloom with a conidial suspension of Botrytis cinerea.Inoculated plants were then incubated in a dew chamber for two days at 20°C and 100% RH. Flower stage was rated at the beginning of the study and two weeks after inoculation. Botrytisdisease symptoms were scored two weeks after inoculation on a visual scale of 0 to 7. Susceptibility to Botrytis blossom blight was greatest on more developed flowers. Buds inoculated at stage 2 through stage 3 (prebloom) developed few disease symptoms, while flowers inoculated at stages 5 to 7 (full bloom) developed more severe symptoms. ‘Magnolia,’ ‘Premier,’ and ‘Tifblue’ flowers at stage 6 were very susceptible. When averaged over the more susceptible flower stages (5, 6 and 7), ‘Jubilee’ and ‘Premier’ had the lowest disease severity scores. ‘Tifblue’ had higher disease scores than ‘Magnolia’ and ‘Climax.’ The two southern highbush cultivars did not differ as a group from the three rabbiteye cultivars in their susceptibility to Botrytisblossom blight. Since susceptibility of blueberry flowers is greatest at or near full bloom, fungicide applications for Botrytisblight control of southern blueberries should begin at flower stage 4 and continue though stage 6.