Studies were conducted to determine the effect of in-row eastern black nightshade establishment and removal timings in plasticulture tomato on tomato yield loss and nightshade berry production and seed viability. Eastern black nightshade was transplanted at 1, 2, 3, 4, 5, 6, and 12 wk after tomato planting (WAP) and remained until tomato harvest, or was established at tomato planting and removed at 2, 3, 4, 5, 6, 8, and 12 WAP to determine the critical weed-free periods. Eastern black nightshade seed viability increased with berry size and with length of establishment or removal time. The critical weed-free period to avoid viable nightshade seed production was 3–6 WAP. Tomato yield decreased with early weed establishment or with delayed time of weed removal. The critical weed-free period to avoid greater than 20% tomato yield loss for the sum weight of extra large and jumbo grades was 28 to 50 d after tomato transplanting.

Nomenclature: Eastern black nightshade, Solanum ptycanthum Dun. SOLPT; tomato, Lycopersicon esculentum.