The joint action of a plant parasitic nematode, Pratylenchus penetrans (root-lesion nematode), and an insect defoliator, Leptinotarsa decemlineata (Colorado potato beetle), on growth, development, and yield of Solanum tuberosum cv. Superior was studied in the field. Three population densities of P. penetrans were superimposed on each of three population levels of L. decemlineata. The major impa...