 Phloem necrosis also is easily observed as dark concentric rings or linear streaks in cross section or longitudinal section of the taproot, respectively.Although crop failures are rare today, curly top is still a potentially problematic issue for sugar beet production in several areas of the western United States The disease has been for the most part confined to the western half of the North American continent and is generally more severe west of the continental divide.It does occur sporadically in the beet-growing areas of the high plains east of the Rocky Mountains, but is not often an economically limiting factor.