Application technology and environmental considerations for use of entomopathogenic nematodes in biological control

A wide range of technology is available for application of entomopathogenic nematodes including various irrigation systems and spray equipment. The choice of application equipment, and manner in which the nematodes are applied, can have substantial impact on pest control efficacy. For example, nozzle or pumping system types are some of the parameters that can affect nematode performance following spray applications. Operating pressures for some nematode species may reach up to 2000 kPa without notable damage, whereas other species may require lower pressure limits, e.g., 1380 kPa for Heterorhabditis megidis. In addition to application equipment, a variety of other abiotic and biotic factors must be considered. In general, a rate of 25 infective juvenile nematodes/cm² is required for successful pest suppression. Critical environmental factors include avoidance of ultraviolet radiation, adequate soil moisture, and appropriate temperature. Certain fertilizers and chemical pesticides can have positive effects on entomopathogenic nematode efficacy, whereas other agents may have neutral or negative effects. Similarly, certain biotic agents present during soil applications can be expected to be detrimental to nematode applications (e.g., nematophagous mites and fungi), whereas other organisms may be beneficial (e.g., some combinations with Bacillus thuringiensis). With some exceptions foliar applications have been less successful than soil applications due to nematode susceptibility to desiccation and UV; recent research, however, indicates that frequent low-rate applications of nematodes to foliage can result in substantial suppression of greenhouse pests such as thrips. Further innovation in application technology will undoubtedly contribute to the expansion of entomopathogenic nematodes as biocontrol agents.