Between Dutch organic growers the late blight problems led to discussions in which a temporary registration of copper products is also suggested. In the research program to stimulate organic production the choice was made also to investigate the efficacy of copper and other products that are allowed in neighbouring countries in organic farming. In the experiment of 2008 different copper containing products were tested. In 2009 this was repeated with the same products, but also other doses and combinations. In 2010 the most important objective of the experiment was to investigate the possibilities of a maximum of 300 gram copper per hectare, divided in different parts, in combination with a decision support system. 300 gram copper was based on the amount different crops need in a six year organic rotation. Except a standard copper product also a copper product used in organic farming in the Netherlands as a leaf fertilizer was used and some products financed by the industry
