Technical Abstract: Alfalfa (Medicago sativa L.) is a highly attractive plant host to Lygus spp. and is used as a trap crop in California organic strawberries to influence the dispersion and dispersal of these pests, particularly L. hesperus. The abundance and distribution of Lygus spp. nymphs between two trap crops separated by 50 strawberry rows was analyzed in 2008 and 2010. Nymphs demonstrated a bimodal distribution in strawberries between trap crops, where nymphs were most abundant and aggregated in alfalfa, when compared with interior strawberry rows, where nymphs were less abundant and randomly distributed. The majority of nymphs were concentrated in trap crops and nymphal densities in interior strawberry rows were well below economic thresholds. Targeting nymphs for control in alfalfa trap crops is recommended. The movement of Lygus spp. from a marked alfalfa trap crop into adjacent strawberry rows or trap crops was also studied in 2008 and 2009 using a chicken egg albumin enzyme-linked immunosorbent assay (ELISA) mark-capture technique. The majority of marked-captured L. hesperus adults and Lygus spp. nymphs remained in alfalfa trap crops, rather than dispersing out into strawberry rows at 24 h, 48 h and 2wks, post protein application. The attenuation of Lygus spp. movement by alfalfa in organic strawberries is a key component of successful trap cropping. Conversely, a small percentage of marked adults and nymphs were captured in neighboring alfalfa trap crops, located 62 m from the point of protein application, highlighting the dispersal capacity of this key pest.