Weed Seed Production as Influenced by Glyphosate Applications at Flowering Across a Weed Complex

Abstract

Late-season weed infestations often do not affect yields and are allowed to mature and contribute seed to the soil seedbank, ensuring the future establishment of competitive weed complexes. Effective long-term weed management strategies must incorporate practices to reduce late-season weed seed production by weed complexes. Field studies were conducted to determine the effects of late-season glyphosate applications on seed production of barnyardgrass, Palmer amaranth, pitted morningglory, prickly sida, and sicklepod. Although sequential 0.42-kg ae/ha glyphosate applications initiated when the first weed species in the complex flowered and repeated every 10 d was the most effective treatment and reduced seed production of all species by ≥ 95%, the most practical treatment was a single 0.84-kg/ha glyphosate application at pitted morningglory flowering, suppressing seed production of barnyardgrass, Palmer amaranth, pitted morningglory, prickly sida, and sicklepod by 88, 83, 98, 95, and 99%, respectively. This research demonstrates that annual contributions by a weed complex to the soil seedbank can be significantly and practically reduced by a single late-season glyphosate application.Nomenclature: Glyphosate, barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG, Palmer amaranth, Amaranthus palmeri S. Wats AMAPA, pitted morningglory, Ipomoea lacunosa L. IPOLA, prickly sida, Sida spinosa L. SIDSP, sicklepod, Senna obtusifolia L. CASOB