Giant ragweed is one of the most competitive annual broadleaf weeds in soybean production fields in the midwestern United States and eastern Canada because of its early emergence, rapid growth rate, high plasticity, and resistance to glyphosate and acetolactate synthase inhibitors. Therefore, early-season management of giant ragweed is critical to avoid yield loss. The objectives of this study were to evaluate control of glyphosate-resistant giant ragweed through the integration of preplant tillage or 2,4-D; PRE or early POST (EPOST) followed by (fb) late POST (LPOST) herbicide programs with or without preplant tillage or 2,4-D; and their effect on soybean injury and yield. A field study was conducted in 2013 and 2014 in David City, NE in a field infested with glyphosate-resistant giant ragweed. Preplant tillage or 2,4-D application provided > 90% control of glyphosate-resistant giant ragweed 14 d after preplant treatment. Giant ragweed control and biomass reduction were consistently > 90% with preplant tillage or 2,4-D fb sulfentrazone plus cloransulam PRE or glyphosate plus cloransulam EPOST fb glyphosate plus fomesafen or lactofen LPOST compared with ≤ 86% control with same treatments without preplant tillage or 2,4-D. PRE or EPOST fb LPOST herbicide programs preceded by preplant treatments resulted in giant ragweed density < 2 plants m−2 and soybean yield > 2,400 kg ha−1 compared with the density of ≥ 2 plants m−2 and soybean yield < 1,800 kg ha−1 under PRE or EPOST fb LPOST herbicide programs. The contrast analysis also indicated that preplant tillage or 2,4-D fb a PRE or POST program was more effective for giant ragweed management compared with PRE fb POST herbicide programs. Integration of preplant tillage would provide an alternative method for early-season control of giant ragweed; however, a follow up application of herbicides is needed for season-long control in soybean.
Nomenclature: 2,4-D amine; cloransulam; fomesafen; lactofen; sulfentrazone; giant ragweed, Ambrosia trifida L.; soybean, Glycine max (L.) Merr.
Ambrosia trifida es una de las malezas de hoja ancha más competitivas en campos de producción de soja en el centro-oeste de los Estados Unidos y en el este de Canada debido a su emergencia temprana, alta tasa crecimiento, alta plasticidad, y resistencia a glyphosate e inhibidores de acetolactate synthase. Por esta razón, el manejo de A. trifida, temprano durante la temporada de crecimiento, es crítico para evitar las pérdidas de rendimiento. Los objetivos de este estudio fueron evaluar el control de A. trifida resistente a glyphosate mediante la integración de labranza en pre-siembra o 2,4-D; aplicaciones PRE o POST temprana (EPOST) seguido por (fb) programas de herbicidas en POST tardía (LPOST) con o sin labranza en pre-siembra o 2,4-D; y su efecto sobre el daño y rendimiento de la soja. Se realizó un estudio de campo en 2013 y 2014 en David City, Nebraska en un campo infestado con A. trifida resistente a glyphosate. La labranza en pre-siembra o la aplicación de 2,4-D brindó >90% de control de A. trifida resistente a glyphosate 14 d después del tratamiento pre-siembra. El control y la reducción en la biomasa de A. trifida fueron >90% consistentemente con la labranza pre-siembra o 2,4-D fb sulfentrazone más cloransulam PRE o glyphosate más cloransulam EPOST fb glyphosate más fomesafen o lactofen POST al compararlo con ≤86% de control con los mismos tratamientos sin labranza pre-siembra o 2,4-D. Programas de herbicidas PRE o de EPOST fb L
