Het blauw groeien van tulpebollen

Abstract

With some tulip varieties brown necrotic spots appear in the bulb scales during the development of the new bulb. These spots are never noticed in the outer living scale, which afterwards becomes the dead skin of the bulb, but always in the underlying scale. In practice this phenomenon is called the blueing of the tulip bulb, because one notices these spots when looking through the outer living scale. The first symptoms appear about the time when the new bulb enters its period of maximum development. Considering the results of experiments to date, it seems unlikely that a fungus or bacterium is responsible for the disease. Nor has it been possible to demonstrate a virus, so the disease would appear to be of a physiological nature. There is an apparent correlation between growth (increase of weight) and the disease. Factors which diminish the growth also reduce the percentage of the disease in the bulbs. The influence of manuring can probably be explained in this way. Application of B, Co, Cu, Mg, Mn, Mo and Zn salts has no influence upon the disease, so there would appear to be no likelihood of the disease being a deficiency disease. The real nature of the disease is still unknown.