In two areas of Jamaica West Indies, a rootstock disease was observed on dying four-year-old Valencia trees budded on Rough lemon. Woody knots of varying sizes were prevalent throughout the root crown of the tree up to the bud-union, and werde strikingly similar to those caused by Sphacropsis knot on Rough lemon. At the Botany Department of the Unviersity of the West Indies, isolation experiments yielded cultures of the fungus Sphaeropsis tumefaciens Hedges from knots cut off the Rough lemon rootstock. Subsequent inoculation experiments (with isolates obtained from woody knots) resulted in knot formation on most of the inoculated branches of Rough lemon, West Indies lime, and Ortanique (a natural cross of tangerine x orange). The disese was observed in a few dying trees of a smal Valencia grove in Rose Hall, Linstead, in St. Catherine, and in Lennox Estates, in Protugal, where it was estimated to have killed 40% of the four-year-old Velencia trees. Control of the disease was obtained by burning all disesed trees.
