| The objectives of this field study were to determine: (1) if seed predation of redroot pigweed plants occurs in agricultural fields; (2) if corn cropping patterns can be manipulated to influence the quantity of weed seed predation; and (3) if microclimatic variation induced by canopy alteration affects the quantity of weed seed predation. Corn was planted in standard (75 cm) or narrow (37.5 cm) rows with corn seedling densities ranging from low to very high (2.5 to 10 plants m−2). The extent of seed predation occurring on Amaranthus retroflexus L. (Amaranthaceae) (redroot pigweed) by Coleophora lineapulvella Chambers (Lepidoptera: Coleophoridae) was evaluated. Predation levels were highly variable spatially and temporally. Seed predation was higher in 2000 than in 1999 (p < 0.05). On average, C. lineapulvella attacked 11% of the inflorescences in 2000 and 3% of inflorescences in 1999. The proportion of damaged seed per attacked inflorescence reached up to 93% in 2000 and up to 42% in 1999. Row spacing and corn density did not affect levels of weed seed predation (p > 0.05) for both years of the study. However, canopies of closely spaced corn increased shading to redroot pigweed plants growing below the canopy, consequently decreasing total weed biomass and seed production. |
