Two of four sweet corn plantings, each with a broad spectrum of weed abundance in plots 3 rows by 6 m, showed a positive relationship of ear infestation by European corn borer,Ostrinia nubilalis(Hübner), with total weed biomass sampled 5 wk after corn seedling emergence. The relationship was more apparent with wider row spacing (91 versus 76 cm) and without cultivation. With the dominant weedsDigitaria sanguinalis, Panicum dichotomiflorum, Amaranthus retroflexus, andChenopodium album, linear regression showed an increase from about 20% ear infestation in weedless plots to about 40% infestation in plots with 2,000 kg/ha above-ground dry weight of weeds at week 5 postemergence. The effect may vary with weed species, and the data show a stronger correlation with forb abundance than with grasses. Sweet corn growers would profit economically by avoiding weedy areas of fields when partial harvests are undertaken in infested plantings.