Efficacy of a copper-based bactericide in controlling bacterial blight of grapevines caused by Xylophilus ampelinus
Xylophilus ampelinus, the cause of bacterial blight of grapevine, was first identified in 2009 in Hokkaido, Japan. We investigated the distribution of X. ampelinus in grapevines and its winter habitat in Hokkaido. After defoliation of artificially infected potted plants, new branches were cut and stored in plastic bags at 5 °C in the dark for 60 days. PCR analysis of samples from the stored branches using a pathogen-specific primer set detected X. ampelinus in the axillary buds but not in the epidermis and vascular bundle. In the naturally infected vineyards, we confirmed the presence of X. ampelinus in the axillary buds and in the vascular bundles at defoliation. However, the pathogen DNA was not detected in the vascular bundles or sap after overwintering. In contrast, the detection frequency in whole axillary buds decreased only slightly, even after overwintering. Additionally, the bacteria were detected in cold-stored bracts and wool at a higher frequency than in the interior axillary bud tissues. Our findings indicate that X. ampelinus likely is not maintained inside tissues or sap and that it might not survive on plant surfaces; rather, bacteria can be found on the underside surface of the bract and bud wool during winter in Hokkaido.