Observations on the introduction of Verticillium chlamydosporium and other parasitic fungi into soil for control of the cereal cyst‐nematode Heterodera avenue

SUMMARY Isolates of Verticillium chlamydosporium and a sterile fungus added to soil on ground oat grain reduced the numbers of Heterodera avenae on wheat by between 26 and 80%. Nematode populations in uninoculated soil increased from 15 eggs/g soil before planting to 218 eggs/g after harvest. V. chlamydosporium was isolated from oat grain that had been air‐dried and milled before introduction into soil. Applications of the fungi on attapulgite clay or as suspensions of mycelium and spores in water had no effect on nematode multiplication. The effect of the fungi on numbers of H. avenae eggs was similar in autoclaved and non‐sterilised soil. V. chlamydosporium added on attapulgite clay to a calcareous sand and a calcareous silty loam could be re‐isolated after at least 6 months. Some isolates colonised the roots of wheat without causing lesions or affecting the dry weights of shoots or roots. These results indicate that V. chlamydosporium may be useful for the biological control of cyst nematode pests.