An experiment was conducted at one location in 1999 and two locations in 2000 to determine the critical weed-free period for peach in North Carolina. The cultivars for the three locations were ‘Contender’, ‘Norman’, and ‘Summerprince’. Weed-free intervals of 0, 3, 6, 9, 12, and 15 wk after peach tree bloom were established. Paraquat at 1.1 kg ai/ha plus nonionic surfactant at 0.25% v/v was applied every 10 d, after treatments were initiated at peach bloom, to maintain weed-free plots. Large crabgrass, hairy vetch, and smooth crabgrass were the primary weeds in Contender. Horseweed, smooth crabgrass, and large crabgrass were the primary weeds in Norman. Bermudagrass, smooth pigweed, and common lambsquarters were the primary weeds in Summerprince. No differences in trunk cross-sectional area were observed between the weed-free periods. Maintaining the orchard floor weed-free for 12 wk after peach tree bloom resulted in the greatest fruit size (individual fruit weight and diameter), total yield, and fruit number.

Nomenclature:Paraquat, bermudagrass, Cynodon dactylon (L.) Pers. CYNDA, common lambsquarters, Chenopodium album L. CHEAL, hairy vetch, Vicia villosa Roth. VICVI, horseweed, Conyza canadensis (L.) Cronq. ERICA, large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA, smooth crabgrass, Digitaria ischaemum (Schreb.) Muhl. DIGIS, smooth pigweed, Amaranthus hybridus L. AMACH, peach, Prunus persica (L.) Batsch., ‘Contender’, ‘Norman’, and ‘Summerprince’