Searching for the cause of clover fatigue

Summary

There is little knowledge about the situation concerning clover fatigue in Norway. Clover is important in organic farming systems and problems with growing legumes will influence organic farming negatively. Both nematodes and fungi can cause clover fatigue. Plant parasitic nematodes were present in samples taken on organic farms in Norway 2011-2012. In 2014 clover plants and soil from 11 farms in Mid-Norway were analysed for both nematodes and fungi. All samples were infected with root rot Fusarium spp., mostly F. avenaceum. Plant parasitic nematodes were found in soil from all samples. Eight nematode groups were present. Spiral nematodes were the most common and abundant group; present on all the farms. No strong correlations were found between numbers of nematodes in the soil and the degree of Fusarium root rot or percentage of clover. However, the least severe root rot was found in the youngest leys.