The combination of keratin hydrolysate with viable cells or infectious propagules of a fungal biological control agent such as Paecilomyces species, Metarhizium species, Beauveria species, and/or Verticillium species, provides effective control of soil-dwelling or subterranean insects, including termites, and particularly those belonging to the family Rhinotermitidae, such as the Formosan subterranean termite and native North American subterranean termites. In use, a foam-forming composition comprising the keratin hydrolysate and an insecticidally effective amount of the fungus are applied to the insects, the locus of the insects, to material susceptible to infestation by said insects, or to the locus of material susceptible to infestation by said insects.