Anecic earthworms (e.g., nightcrawlers) create deep, vertical burrows and feed by dragging organic matter from the soil surface into the burrow, thereby incorporating organic matter. The incorporation of leaf litter in orchards may reduce inoculum levels of organisms that cause diseases such as apple scab. However, anecic earthworms are generally absent from agro-ecosystems in California, in part possibly because of low rainfall and seasonal drought. Anecic earthworms (Lumbricus terrestris) were introduced to an organic apple orchard in Watsonville, California, where the resident earthworm community included only the endogeic (subsurface-feeding) species Aporrectodea caliginosa and Microscolex dubius. With L. terrestris present, incorporation of apple leaf litter increased from less than 28% to 79%. Yearly patterns of activity of resident earthworm species were unimodal, corresponding to the winter season of peak rainfall and low soil temperature. Earthworm populations were similar for organic and conventional treatments until the third year, when abundance and biomass of resident species were significantly greater in the organic plots.