Herbicide Tank Mixtures for Broad-Spectrum Weed Control in Florida Citrus

Abstract Weed control in Florida citrus is primarily based on herbicides. Saflufenacil, a POST-applied herbicide is recently registered for broadleaf weed control in citrus. Saflufenacil has very limited grass activity; therefore, it should be tank mixed with graminicides or broad-spectrum herbicides to increase the spectrum of weed control. Greenhouse and field experiments were conducted at two locations (Polk County and Orange County, FL) to evaluate the efficacy and potential antagonism or synergy of saflufenacil and sethoxydim applied alone or tank mixed, and various two- and three-way mixes with glyphosate or pendimethalin. The results suggested that tank mixing saflufenacil and sethoxydim had neither synergistic nor antagonistic effect on broadleaf and grass weed control, respectively. Tank mixing pendimethalin with saflufenacil and sethoxydim improved broadleaf and grass weed control and reduced weed density and biomass, compared with saflufenacil or sethoxydim applied alone or tank mixed at 45 and 60 d after treatment (DAT). Glyphosate tank mixed with saflufenacil and sethoxydim provided > 90% control of broadleaf and grass weeds at 15 DAT, reduced density ≤ 8 plants m−2, and reduced biomass < 95 g m−2 at 60 DAT. Glyphosate applied alone was less effective than it was when tank mixed with saflufenacil and sethoxydim or pendimethalin for broadleaf and grass weed control, indicating an additive effect of tank mixture on glyphosate efficacy. It is concluded that saflufenacil can be tank mixed with sethoxydim for control of broadleaf and grass weeds without antagonism on the efficacy of either herbicide; however, tank mixing saflufenacil and sethoxydim with glyphosate or pendimethalin provided long-term, broad-spectrum weed control in Florida citrus. Nomenclature: Glyphosate; pendimethalin; saflufenacil; sethoxydim; citrus, Citrus spp. Resumen El control de malezas en cítricos en Florida está basado principalmente en herbicidas. Saflufenacil, un herbicida aplicado POST, fue registrado recientemente para el control de malezas de hoja ancha en cítricos. Saflufenacil tiene actividad muy limitada sobre gramíneas; por lo que debe ser mezclado en tanque con graminicidas o herbicidas de amplio espectro para incrementar el espectro de control de malezas. Se realizaron estudios de invernadero y de campo en dos localidades (condados Polk y Orange en Florida) para evaluar la eficacia y el antagonismo o sinergismo potencial de saflufenacil y sethoxydim aplicados solos o en mezcla en tanque, y varias mezclas en dos y tres formas con glyphosate o pendimethalin. Los resultados sugirieron que mezclar en tanque saflufenacil y sethoxydim no tuvo efectos sinérgicos ni antagónicos en el control de malezas de hoja ancha o gramíneas, respectivamente. El mezclar en tanque pendimethalin con saflufenacil y sethoxydim mejoró el control de malezas de hoja ancha y gramíneas y redujo la densidad y biomasa de malezas a 45 y 60 días después del tratamiento (DAT), en comparación con saflufenacil o sethoxydim aplicados individualmente o en mezcla en tanque. Glyphosate mezclado en tanque con saflufenacil y sethoxydim brindó >90% de control de malezas de hoja ancha y gramíneas a 15 DAT, redujo la densidad ≤8 plantas m−2 y redujo la biomasa <95 g m−2 a 60 DAT. Glyphosate aplicado solo fue menos efectivo que cuando se aplicó en mezcla en tanque con saflufenacil y sethoxydim o pendimethalin para el control de malezas de hoja ancha y gramíneas indicando un efecto aditivo de la mezcla en tanque sobre la eficacia de glyphosate. Se concluye que saflufenacil puede ser mezclado en tanque con sethoxydim para el control de malezas de hoja ancha y gramíneas sin causar antagonismo sobre la eficacia de ninguno de estos herbicidas. Sin embargo, el mezclar en tanque saflufenacil y sethoxydim con glyphosate o pendimethalin brindó un control de amplio espectro de malezas de larga duración en cítricos en Florida.

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