Influence of aqueous extracts of organic matter on the sensitivity of Heterodera schachtii Schmidt and Meloidogyne incognita (Kofoid and White) Chitwood eggs to Verticillium chlamydosporium Goddard infection

Sugar beet cyst and root-knee nematode eggs were exposed to different conce ntrations of aqueous compost extracts from the following commercial organic amendments: algae, earthworm, pine tree bark, medicinal and spice herbs, g rape husk and poultry manure as well as re noncomposted neem cake. Eggs wer e treated with the extracts for 3 min and were then challenged with the egg pathogen Verticillium chlamydosporium to detect changes in sensitivity to egg infection caused by active substances in the extracts affecting the egg shell. Exposure to the extracts significantly (P = 0.05) increased the sen sitivity of Meloidogyne incognita and Heterodera schachtii eggs to Fungal i nfection. Sensitivity of cyst nematode eggs to V. chlamydosporium infection increased from 18 in the control to 46 and 49 % following treatment with p oultry manure compost and neem cake extracts, respectively. Infection of ro ot-knot eggs increased two fold over the controls when exposed to pine tree bark compost extract. A positive relationship between egg sensitivity to f ungal infection and the concentration of aqueous extracts was detected. The se results demonstrate that hydrophilic secondary metabolites in the aqueou s extracts of composed organic soil amendments increase egg susceptibility to fungal egg pathogens. These compounds may alter or degrade the egg shell or distort the egg membrane chat protects the eggs, making them more sensi tive to fungal antagonists.