Persistence of the nematophagous fungus Paecilomyces lilacinus strain 251 in soil under controlled conditions

Abstract

The persistence of the nematophagous fungus Paecilomyces lilacinus Samson strain 251 (PL251) and the effect of application rate, substrate type, as well as the presence of the nematode host on its dynamics after application to the soil were investigated under controlled conditions. In all experiments, increase of P. lilacinus colony forming units after application was not found. In contrast, a gradual decline in fungal densities over time was observed. Application rate had no significant effect on the dynamics of the fungal population. Likewise, P. lilacinus density decline in soil was not significantly affected by the presence of the nematode host. Substrate type had a significant effect on P. lilacinus persistence in soil. The fungal agent persisted longer in silty loam and clay soil, with reduced persistence when sand was added to field soil. Conversely, when organic substrate was added to pure sand, persistence was significantly increased. Although persistence of fungal biocontrol agents in soil depends on various biotic and abiotic conditions, baseline data on persistence such as those reported in this study are helpful for biocontrol and environmental risk assessment and merit further study.

Keywords:

• biological control
• Paecilomyces lilacinus
• persistence
• plant-parasitic nematodes

Acknowledgements

The authors would like to thank K. Schmidt for statistical advice and A. Nilgen for technical assistance. Prophyta Biologischer Pflanzenschutz GmbH, Germany is acknowledged for providing samples of commercially formulated P. lilacinus strain 251.