Behavior of pyriftalid in soil and its phytotoxic activity on Echinochloa oryzoides seedlings emerging from various soil depths

Abstract

The phytotoxic activity of pyriftalid ([RS]-7-[4,6-dimethoxypyrimidin-2-ylthio]-3-methyl-2-benzofuran-1[3H]-one) on barnyard grass (Echinochloa oryzoides) seedlings emerging from various depths in the soil was investigated in relation to its behavior in the soil.The growth of the barnyard grass seedlings in the soil mixed with pyriftalid was inhibited, depending on the concentration of the herbicide in the soil water but not on the amount in the total soil. A topmost pyriftalid-treated layer was formed by applying the herbicide to the soil surface under water-leakage conditions.The concentration of pyriftalid in the soil water and the amount that was adsorbed on the soil solid decreased with time, but the decrease was more marked in the pyriftalid concentration in the soil water than in the amount that was adsorbed on the soil solid.The emergence time of barnyard grass in the soil was faster in the seeds that were located in the shallower soil layer, compared to the deeper soil layer. The growth inhibition of the barnyard grass seedlings emerging from the shallower soil layer was greater than that of the barnyard grass seedlings emerging from the deeper soil layer after the soil surface application of pyriftalid. It is suggested that the emergence timing from the different soil depths is an important factor affecting the herbicidal activity of pyriftalid when it is applied to the soil surface under paddy field conditions.

Herbicide‐resistant weeds in the Philippines: Status and resistance mechanisms

“…Examples of the herbicides that were introduced after the 1990s for grass control include thenylchlor, cafenstrole, flufenacet, fluthiamide, fentrazamide, indanofan, dithiopyr, thiazopyr, pyributicarb, oxadiargyl, pentoxazone, clethodim, butroxydim, pyriminobac, pyribenzoxim, etobenzamid and cumyluron. New herbicides that were introduced for grass control in the 2000s include pyriftalid, clefoxydim, metamifop, oxaziclomefone, flucetosulfuron and propyrisulfuron (Takahashi et al 2000;Tomlin 2000;Kanzaki et al 2001;Morita 2003;Kobayashi et al 2004;Murano et al 2007;Kobayashi & Tsunekawa 2010;Ikeda et al 2011;Krämer et al 2012;Lainsbury 2013). New herbicides with new modes of action are inhibitors of the enzymes that are involved in pigment synthesis and include protoporphyrinogen oxidase, deoxy-D-xylulose-5-phosphate synthase, hydroxyphenylpyruvate dioxygenase, phytoene desaturase and the inhibitors of cellulose biosynthesis (Krämer et al 2012).…”

5,5′-Thiobis(3-bromoisothiazole-4-carbonitrile)

“…Heterocycle sulfides are a particularly important group of compounds with numerous examples of biologically useful compounds such as the immunosuppressant Azathioprine 1 [1][2][3], the antibacterial drug meropenem 2 [4][5][6] and the herbicide pyriftalid 3 [7][8][9] (Figure 1). Focusing on isothiazole sulfides, there are several examples of biologically useful compounds such as the 4-cyanoisothiazole 4 that has shown antiviral activity against polio [10][11][12] and dithiine 5 which is active as an antifungal agent [13] (Figure 1).…”