Bladschade bij potanthurium

Sensitive potanthurium cultivars can show leaf damage that reduce both the ornamental and the market value of the product. The costs for the sector are estimated at € 7,500 per hectare per year. To study the possible causes of two types of leaf damage, a series of activities and experiments were performed between November 2011 and May 2012. It has been found that the necrotic spots on the leaf edge (appearing mainly in older leaves) do not always correspond with guttation and / or damage to the hydathodes. The necrosis, a non reversible damage is not caused by calcium deficiency or excess manganese, on the contrary, a higher calcium supply leads to an increased damage. Yellow spots on the younger leaves, the other type of damage, has proved reversible and is not the result of lensing of water droplets on the leaf. A reduced supply of magnesium or manganese, worsen the damage. Both damage forms have been largely prevented by cultivation in a different environment (under foil), the transition from a humid environment (under foil) to a “normal” environment gradually leads to an increase of the damage symptoms. However, growing under plastic also has negative effects. It is therefore recommended to conduct further research to the influence of the relations between the watering strategy and the substrate moisture and the occurrence of the damage.