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MCPA Synergizes Imazamox Control of Feral Rye (Secale cereale)

  • Andrew R. Kniss (a1), Drew J. Lyon (a2), Joseph D. Vassios (a3) and Scott J. Nissen (a3)

Field, greenhouse, and laboratory studies were conducted to determine the effect of MCPA ester, fertilizer type, and fertilizer rate on feral rye control with imazamox. In field studies near Sidney, NE, increasing the concentration of liquid ammonium phosphate (10–34–0) from 2.5 to 50% of the spray solution decreased feral rye control with imazamox by as much as 73%. Conversely, adding MCPA ester to imazamox significantly increased feral rye control in field studies by up to 77%. Initial greenhouse studies confirmed the liquid ammonium phosphate antagonism effect, but subsequent greenhouse studies were inconsistent with regard to the interaction between fertilizer and imazamox. At least one source of liquid ammonium phosphate was shown not to be antagonistic, and therefore fertilizer source or contaminants may be responsible for initial field observations. Greenhouse studies confirmed the synergistic interaction between MCPA and imazamox. MCPA ester applied at 560 g ai ha−1 decreased the rate of imazamox required to cause 50% reduction in feral rye dry weight (GR50) to 13 g ha−1 compared to 35 g ha−1 for imazamox alone. Although addition of MCPA ester increased 14C-imazamox absorption by 8% in laboratory studies, less 14C translocated out of the treated leaf; therefore the mechanism of synergism does not appear to be related to imazamox absorption or translocation.

Se realizaron estudios de campo, invernadero y de laboratorio para determinar el efecto de MCPA éster y tipo y dosis de fertilizante en el control de Secale cereale silvestre con imazamox. En los estudios de campo cerca de Sidney, Nebraska, el incremento de la concentración de fosfato de amonio líquido (10-34-0) de 2.5 a 50% de la solución asperjada, disminuyó el control de S. cereale con imazamox hasta 73%. Por otra parte, la adición de MCPA éster al imazamox incrementó significativamente el control del S. cereale silvestre hasta 77%, en los estudios de campo. Los primeros estudios de invernadero confirmaron un efecto antagónico del fosfato de amonio líquido, pero estudios subsecuentes fueron inconsistentes con respecto a la interacción entre el fertilizante e imazamox. Al menos una fuente de fosfato de amonio líquido no mostró ser antagónica y por lo tanto la fuente del fertilizante o algún contaminante podrían ser los responsables de las primeras observaciones en campo. Los estudios de invernadero confirmaron la interacción de sinergismo a entre MCPA e imazamox. MCPA éster aplicado a 560 g ia ha−1 disminuyó la GR50 de imazamox 63%, en comparación con imazamox solo. En estudios de laboratorio, aunque la adición de MCPA éster incrementó la absorción de 14C-imazamox en 8%, menos 14C se translocó fuera de la hoja tratada; por lo tanto, el mecanismo de sinergismo no parece estar relacionado a la absorción o translocación de imazamox.

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Weed Technology
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