Bispyribac-sodium {sodium 2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxy] benzoate} has recently been introduced to California where it effectively controls Echinochloa spp. in rice (Oryza sativa L.). However, biotypes of early watergrass (Echinochloa oryzoides (Ard.) Fritsch) and late watergrass (E. phyllopogon (Stapf ) Koss.) have evolved resistance to this herbicide. In 2001 and 2002, greenhouse and field experiments evaluated interactions between thiobencarb {S-[(4-chlorophenyl) methyl] diethylcarbamothioate} and bispyribac-sodium on resistant (R) and susceptible (S) late watergrass in California rice. Synergism was assessed using Colby’s test and regression analysis. In the greenhouse, thiobencarb at 4480 and 5333 g ai ha-1 synergistically reduced bispyribac-sodium GR50 values on the R and S biotypes by 50–70% without increasing toxicity to rice. Synergism was also observed on S late watergrass in the field when 10 g ai ha-1 bispyribac-sodium was mixed with 1120–2240 g ai ha-1 thiobencarb. These effects could be related to interactions between thiocarbamates and enzymes in Phase I reactions of herbicide metabolism. This synergism results in better control at lower rates allowing a reduction in weed control costs, the herbicide load on the environment and a lower selection pressure towards resistant weed biotypes.
Enhanced effect of thiobencarb on bispyribac-sodium control of Echinochloa phyllopogon (Stapf) Koss. in California rice (Oryza sativa L.)
VIDOTTO, Francesco;
2004-01-01
Abstract
Bispyribac-sodium {sodium 2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxy] benzoate} has recently been introduced to California where it effectively controls Echinochloa spp. in rice (Oryza sativa L.). However, biotypes of early watergrass (Echinochloa oryzoides (Ard.) Fritsch) and late watergrass (E. phyllopogon (Stapf ) Koss.) have evolved resistance to this herbicide. In 2001 and 2002, greenhouse and field experiments evaluated interactions between thiobencarb {S-[(4-chlorophenyl) methyl] diethylcarbamothioate} and bispyribac-sodium on resistant (R) and susceptible (S) late watergrass in California rice. Synergism was assessed using Colby’s test and regression analysis. In the greenhouse, thiobencarb at 4480 and 5333 g ai ha-1 synergistically reduced bispyribac-sodium GR50 values on the R and S biotypes by 50–70% without increasing toxicity to rice. Synergism was also observed on S late watergrass in the field when 10 g ai ha-1 bispyribac-sodium was mixed with 1120–2240 g ai ha-1 thiobencarb. These effects could be related to interactions between thiocarbamates and enzymes in Phase I reactions of herbicide metabolism. This synergism results in better control at lower rates allowing a reduction in weed control costs, the herbicide load on the environment and a lower selection pressure towards resistant weed biotypes.
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