| Diseases: Toppling, leaf toppling and flower spots |  |
Abnormalities of non parsitaire or unknown cause
Nearing the end of the greenhouse period a dark green, glazy zone will develop in the stem; often drops of moist will come out at this spot. Therefore this disease is also called ‘water stems’. After some time the tissue will loose its firmness, it will shrivel and the stem will bend at that spot (toppling). These symptoms can develop everywhere in the stem, but will mostly be found in the upper part of the stem.
The abnormalities can only be found in the greenhouse. Toppling will always occur in that part of the stem that is growing most fast. As the temperature treatment of the bulbs and/or the growing conditions have lead to a very fast stretching of the stem the symptoms will be found earlier and at a lower position of the stem. The chance at toppling increases as the temperature in the greenhouse is higher. A high humidity of the air very clearly stimulates the development of (leaf) toppling. When plants evaporate too little, a lack of calcium will develop in the fastest growing parts. Because of this the porosity of the so-called cell membranes will increase, because of which water will leak from the cells.
A large number of cultivars are sensitive to toppling, like ‘Kees Nelis’, ‘Leen van der Mark’ and double early tulips.
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