Biosurfactants produced by microbes are used to control pests. The biosurfactants can be produced by cultivating a biosurfactant-producing microbe, producing a fermentation broth, and obtaining the biosurfactant from the fermentation broth. Alternately, the biosurfactants can be produced in situ in the environment of the pests by applying a carbon substrate to the pests' environment, which permits naturally-occurring biosurfactant-producing microbes to grow and to generate the biosurfactants. The biosurfactants have pesticidal qualities, and can be used to control a variety of pests, while being biodegradable and otherwise avoiding adverse environmental effects that have often been associated with conventional synthetic pesticides.