Biological control of clover cyst nematode (Heterodera trifolii) with fungi parasitic to nematodes or their eggs

The ability of four fungi to suppress nematode reproduction and ameliorate yield loss of white clover (Trifolium repens) in soil infested with clover cyst nematode (Heterodera trifolii) was examined in a pot experiment. Three fungal parasites of nematode eggs (two sterile fungi and Scolecobasidium constrictum) and a parasite of nematodes (Hirsutella rhossiliensis) were added to soil in the form of alginate beads. At eight weeks after sowing, the mean number of cysts which developed per pot was reduced by Scolecobasidium constrictum, one of the sterile fungi and H. rhossiliensis. H. rhossiliensis also reduced the number of cysts per gram of plant dry matter and maintained dry matter yield per pot and per plant at a level not significantly different from that of control pots (without nematodes) or pots treated with H. rhossiliensis alone. The number of eggs which developed within each cyst was increased in the presence of H. rhossiliensis. Results suggest that fungi such as H. rhossiliensis may have the potential to enhance the establishment of white clover.