Crop tolerance (CT), the crop's ability to endure or avoid competitive stress from weeds, varies between old and modern dent corn hybrids; however, this hypothesis has not been tested in sweet corn. Three modern sweet corn hybrids, known to vary in canopy density, were subjected to a range of wild-proso millet densities under irrigated conditions in Washington and primarily rain-fed conditions in Illinois. A path analysis was used to identify relationships among CT and specific canopy properties important to competitive interactions. Crop tolerance varied among hybrids in three of four site–years. Sweet corn hybrid ‘Spirit’ suffered higher yield losses than hybrids ‘WHT2801’ and ‘GH2547’. Generally higher yield loss parameter estimates in Illinois, compared with Washington, suggests CT may have more to offer for weed management in the north-central than north-western United States. Path analysis indicated that wild-proso millet biomass and seedling population density were both important factors driving yield loss in canopy-sparse Spirit, whereas only early season wild-proso millet population density contributed to yield loss of canopy-dense WHT2801 and GH2547. Differential tolerance to weed interference exists among commercially available sweet corn hybrids.

Nomenclature: Wild-proso millet, Panicum miliaceum L. PANMI, sweet corn, Zea mays L. ‘GH2547’, ‘Spirit’, ‘WHT2801’.