Efficacy Patterns of Biopesticides Used in Potting Media

Greenhouse nursery production represents a large and growing industry. In recent years there has been a shift both toward the use of soilless media and integrated pest management. Application of entomopathogens such as nematodes, fungi, and bacteria against soil-dwelling insect pests is a sustainable alternative to insecticide centered control programs. Soilless media (peat, coir, or bark-based) are designed to provide a plant pathogen free growing environment. The potential impact of soilless media on the efficacy of entomopathogens is often overlooked. In this review, we summarize the findings of research studies in which entomopathogens were applied to control insect larvae or eggs in soilless media. Most studies concentrated on controlling coleopteran larvae, primarily Otiorhynchus sulcatus, and dipteran larvae in the Bradysia genus. Entomopathogenic nematodes appear to perform better in peat–based media, but no clear trend emerged for entomopathogenic fungi. Control of Bradysia spp. was usually around 50% but nematodes fared better in bark–based media. The effect of media may not be as important for fungi and bacteria because they are non-motile organisms, whereas nematodes move along the water film to find the host. However, application method may influence the efficacy of fungi and bacteria. In general, few conclusions can be drawn about the direct effect of media on biological agents and we suggest that detailed information on the physical properties of soilless media be provide in future studies.