Postemergence Control of Glyphosate/Paraquat-Resistant Hairy Fleabane (Conyza bonariensis) in Tree Nut Orchards in the Central Valley of California
2015
Moretti, Marcelo L. | Shrestha, Anil | Hembree, Kurt J. | Hanson, Bradley D.
Hairy fleabane is an important weed in orchards and vineyards of California. Populations of glyphosate-resistant (GR) and glyphosate-paraquat-resistant (GPR) hairy fleabane have been documented in California but very little information is available on the efficacy of other POST herbicides on these populations. Greenhouse and field experiments were conducted to evaluate the efficacy of several POST herbicides registered in almond orchards on GPR, GR, and glyphosate/paraquat-susceptible (GPS) hairy fleabane plants. Plants were treated at the 8- to 12-leaf stage in greenhouse experiments, and at the bolting to flowering stage in field experiments. A sequential application of glyphosate (1,100 g ae ha⁻¹) followed by paraquat (500 g ai ha⁻¹) 14 d later did not control the GPR plants in any of the studies, but was effective in controlling the GR and GPS plants. Glufosinate at 1,050 g ai ha⁻¹ or saflufenacil at 48.8 g ai ha⁻¹ resulted in 90% or greater control of all populations in all studies, whereas glyphosate (1,100 g ae ha⁻¹) + 2,4-D (1,090 g ae ha⁻¹) resulted in inconsistent control (58 to 100%). The GPR population was not resistant to other common POST herbicide modes of action used in California tree nut orchards, and glufosinate and saflufenacil can provide growers effective management options for hairy fleabane in these crops.Nomenclature: 2,4-D; carfentrazone; glufosinate; glyphosate; paraquat; saflufenacil; hairy fleabane, Conyza bonariensis (L.) Conquist; almond, Prunus dulcis (Mill.) D.A. Web.
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