Use of nematodes in the fight against harmful soil insects
The potential for pest control of entomopathogenic nematodes (EPN) that are capable of killing pests living in the soil has not been exhausted. The frequency and the types of these soil micro-organisms have been studied in various habitats and their suitability for use as biological pest control inv
Background (completed research project)
Large-scale application of entomopathogenic nematodes (EPN) in pest control has previously been shown to be cost-inefficient. Deeper knowledge of EPN and development of effective application methods for pest control may change this. This is important in view of climate change, which is leading to invasion of new soil insect pests and therefore to new risks for agricultural crops.
The project investigated the occurrence of EPN in Swiss agricultural soils and in naturally occurring soils and identified the factors that determine their population density and effectiveness as a means of pest control. The compatibility of EPN with other beneficial soil organisms has been studied as part of the Soil Biology Cluster.
Newly developed molecular methods allow very precise identification and quantification of various EPN species occurring in soil samples. EPN numbers in the soils were very low and no significant differences were found between cultivation systems. None of the tested agricultural methods affected the presence or persistence of EPN. Only the use of cover crops showed a minor positive impact.
The main reason for the low EPN numbers probably is the intense competition with other organisms and strong pressures by natural enemies. It is also possible that insufficient numbers of host insects do not allow the EPN to reproduce and build up a persistent population.
EPN were nicely compatible with beneficial bacteria and mycorrhizal fungi. In some cases positive effects on plant performance were observed. An initial field trial indicated a 30% increase in maize yield after combined application of EPN and/or bacteria.
Importance for research
New knowledge has been generated on EPN ecology and the factors that affect their presence. Organically farmed crops showed just as few EPN populations as those that were conventionally farmed with intensive tilling. Competition with other soil organisms and natural enemies are the key factors in impacting EPN populations. In addition, a novel competition with free-living nematodes with EPN inside insect cadavers was revealed.
The presence of EPN in Swiss agricultural soils is insufficient to combat current or emerging soil pest problems, irrespective of the agricultural practices. This implies that for an effective pest control there will have to be supplementation of EPN. Current application methods are too expensive, however, and new methods need to be developed.