Field experiments were conducted to determine density-dependent effects of eastern black nightshade season-long interference on tomato-yield loss when growing in-row with staked plasticulture tomato. Eastern black nightshade was transplanted at densities of zero, one, two, three, four, or five plants per crop plant hole in the plastic. Eastern black nightshade densities of one to five reduced the number and weight of larger fruit grades (threes, extra larges, jumbos, marketables, totals) similarly but did not reduce yields of smaller fruit grades (culls, mediums, and larges) from the weed-free. Eastern black nightshade reduced percent yield loss of jumbo grade, the premium grade, which could be predicted by a rectangular hyperbola model. The value ($ ha−1) of jumbo fruit and the value of the sum of large, extra large, and jumbo grade was reduced at densities of eastern black nightshade as low as one plant per hole.
Nomenclature: Eastern black nightshade, Solanum ptycanthum (Dun.) SOLPT; tomato, Lycopersicon esculentum L.