BARK‐SPLIT–A VIRUS DISEASE OF PLUMS

Abstract

The bark‐split disease of plums commences with necrotic lesions in the outer bark, causing depressions on the surface; these lesions extend in area and depth, resulting in split and roughened bark, and crippling or killing trees of sensitive varieties like Cambridge Gage.The causal virus was transmitted by grafting in the dormant season, but, probably because it is localized in older tissues, it was rarely transmitted or scion‐perpetuated by summer budding.About 90% of Common Plum clonal rootstocks from East Malling Research Station's layer‐beds were found to be infected. Apparently virus‐free Common Plum was propagated by cuttings from the roots of Common Plum under normal Cambridge Gage trees.A different type of bark‐split disease developed on Shiro Plum inoculated with virus from a tree of Quetsche Précoce de Zimmer. Leaf symptoms accompanying infection with this and with the virus from Common Plum were similar.Bark‐split disease is compared and contrasted with diamond canker of French Prune in California, and features that distinguish bark‐split from bacterial canker are described.