Colorado potato beetle (CPB) populations were reduced when potato crops were planted without tillage into various cover crops and/or mulched with supplemental rye straw, in four separate experiments in 2003 and 2004. The response increased with quantity of residue, but apparently differed by cover crop type. A 40% to 90% reduction in CPB numbers was typical in potato crops cover-cropped and/or mulched with rye and/or clover. The pest-suppressive effect may be mediated by impairment of orientation to the crop, increase in arthropod predators due to buffering of the abiotic environment or provision of alternate prey, and/or plant growth enhancement.