Currently, when protecting plants from root-feeding insects using entomopathogenic fungi, efforts are concentrated on applying large amounts of inoculum to increase the fungal population throughout the bulk soil. This technique presents numerous problems including: 1) A requirement for large quantities of fungal inoculum, often making applications uneconomical, 2) It is difficult to get the fungal propagules applied to the soil surface to penetrate into the soil more than a few cm and 3) A large amount of time, money and effort is spent protecting areas of the bulk soil where the pest either does not occur or is not of concern. By developing techniques to use the roots as a delivery system for entomopathogenic fungi, the costs and logistics of biological control would be much more favorable. The ability of Metarhizium anisopliae-treated roots to control black vine weevil, Otiorhynchus sulcatus F., larvae indicates the potential to use colonized roots as a delivery system for fungal biological control agents of root-feeding insects. Regardless of which root-feeding insect is considered, they all feed on plant roots in order to complete their development and thus come into contact with the rhizosphere competent fungus. By using this approach, the application of entomopathogenic fungi should be economical as only the roots of small plants (rooted cuttings, tissue culture) or potentially seeds would have to be inoculated. It is becoming clear that when selecting an entomopathogenic fungal isolate, understanding factors associated with entomopathogen biology outside their insect host may be more important than its virulence in a laboratory bioassay of insect infection.