ABSTRACT
In 2005, the active substance maleic hydrazide was released on the Belgian market. Maleic hydrazide is authorized in potatoes as foliar treatment for instore sprout suppression and control of volunteers. The mode of action is based on blocking cell division whilst cell elongation is not affected. The product must be applied at once during the growing season, only after at least 80% of the tubers have reached 25 mm diameter and not later than 3 weeks before haulm killing. The first 24 h after application, no meaningful precipitation should occur to insure sufficiently uptake of the product by the crop. Field trials were set up for 4 years (2005-2008) and 4 locations per year with application of maleic hydrazide in four different cultivars (Bintje, Fontane, Asterix and Cilena). After application, the cultivar Asterix showed almost every year a temporarily phytotoxicity (bronze discoloration). On the first place yield was determined. When maleic hydrazide was applied too early (80% tubers % 25mm diameter) yield was negatively affected (3 years on 4) except for the cultivar Cilena (fresh market). Internal quality (dry matter and fry quality) was not influenced by the application of maleic hydrazide. Only Fontane had a slightly lower dry matter content. Maleic hydrazide also influenced appearance of secondary growth. However, the results were very variable depending on cultivar, location and time of application. After harvest, the tubers were kept in storage and assessed monthly on germination. Potatoes treated late in the growing season, showed a shorter dormancy period. A part of the tubers was replanted the following spring to verify volunteer control. Additional trials were set up by the Flemish government for two years (2010-2011). The results of previous trials were confirmed. Additional, the influence of maleic hydrazide on internal germination during storage was examined on the cultivar Innovator. The tests clearly showed a positive effect for this parameter.
