Root-knot nematodes are widely distributed throughout the world. Their distribution and economic importance are purported to be related to biological and environmental factors favorable to Meloidogyne spp. A scheme for comparing Meloidogyne spp. with two other genera of diverse biological characteristics is presented to support this hypothesis. It is further suggested that a probability index can be developed to predict the likelihood of a given nematode species being transported, established, and becoming economically important in regions of the world where i t does not already occur.
Keywords: Meloidogyne spp.; distribution; root-knot nematodes.