In nature, there are both pathogenic and non-pathogenic strains of R. rhizogenes. Pathogenic strains are capable of causing hairy root and crown gall. Crown gall is usually associated with Rhizobium radiobacter (formerly known as Agrobacterium tumefaciens). Bacteria are capable of gene transfer and thus some strains of R. rhizogenes have acquired the ability to cause crown galls but R. rhizogenes are most commonly known for causing hairy root (1). Crown gall, usually caused by R. radiobacter, can be an economically important disease of many plants. Non-pathogenic strains of R. rhizogenes can be used as a biological control agent against pathogenic strains of R. radiobacter. Allen Kerr identified the K84 strain of R. rhizogenes (formerly known as A. radiobacter). He discovered that if the K84 strain of non-pathogenic R. rhizogenes was present in high population densities in the soil with pathogenic R. radiobacter then the incidence of crown gall could be significantly reduced. Kerr identified the antibiotic agrocin 84, produced by R. rhizogenes, as the method of control (3). The commercially available biological control agent, Galltrol A, contains R. rhizogenes strain K84.