Botryosphaeria stem blight of southern blueberries: cultivar susceptibility and effect of chemical treatments
2009
Smith, B.J.
Botryosphaeria stem blight, caused by the fungus Botryosphaeria dothidea, is a destructive disease of rabbiteye (Vaccinium ashei) and highbush (V. corymbosum) blueberries in the southeastern United States. The susceptibility of 21 southern highbush and seven rabbiteye blueberry cultivars was compared using a detached stem assay. Succulent, partially-hardened stems were wounded, inoculated with a mycelial block from a 14-day-old culture of B. dothidea, and incubated for 15 days. Disease severity was determined by comparing lesion length with that of the susceptible rabbiteye cultivar Tifblue. Cultivars with a mean lesion length less than that of 'Tifblue' were classified as resistant and included three southern highbush cultivars: Pearl River, Emerald, and Star. Cultivars whose lesion length was equal to or greater than that of 'Tifblue' in both years were classified as susceptible or very susceptible and included eight southern highbush cultivars: Legacy, Gulf Coast, Cooper, Jubilee, Biloxi, O'Neal, Magnolia, and Reveille. In a comparison of wound versus non-wound inoculations, lesion length was significantly greater on stems wounded by removing a small section of bark prior to inoculation than on nonwounded stems or on stems inoculated at a fresh leaf scar. The potential efficacy of fungicides for stem blight control was determined using the detached stem assay. In two studies stems treated with cyprodinil + fludioxonil or pyraclostrobin had shorter lesions than stems receiving no fungicide treatment while stems treated with captan, ziram, and tebuconazole had lesions as long as those receiving no fungicide treatment.
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