Role of underground parts of barnyardgrass (Echinochloa crus‐galli (L.) Beauv. var. formosensis Ohwi) in its sensitivity to thenylchlor in soil

Abstract

In the present study, the phytotoxic activity of top-soil applied with thenylchlor [2-chloro-N -(3-methoxy-2-thieny)-2 ¢ ,6 ¢ -dimethylacetanilide] on the growth of rice ( Oryza sativa L.) was dependent on the emergence depth in soil but its activity on barnyardgrass ( Echinochloa crusgalli (L.) Beauv. var. formosensis Ohwi) was only slightly affected by the emergence depth. However, the phytotoxic activity on barnyardgrass and rice was similar irrespective of the different emergence depths in its treatment to all soil layers. Thenylchlor treatment to the mesocotyl of barnyardgrass induced significant inhibition of shoot elongation, whereas the treatment to the coronal root only inhibited the coronal elongation without inhibiting shoot elongation. Absorption and translocation of 14 C-thenylchlor in barnyardgrass were determined in water culture. The different amounts of radioactivity per plant among the treatments to the underground parts were due to the plant part that came in contact with 14 C-thenylchlor. The radioactivity per dry weight was found to be higher in the basal part of the shoot than in its upper part in all treatments to the underground parts. It was suggested that the phytotoxic activity of thenylchlor on the growth of barnyardgrass in soil is induced by its accumulation in the basal part of the shoot through translocation. This primarily occurs after the absorption substantially by the mesocotyl from the herbicide-treated layer and additionally by other underground parts.

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

“…It also was suggested that the phytotoxic activity of pyriftalid on barnyard grass in the soil is dependent on its concentration in the soil water in the herbicidetreated layer when the absorptive parts of the plant can reach this layer, although the timing of emergence was dominated by the emerging depth in the soil (Mester & Buhler 1990). It is important to emphasize that, regardless of the emerging depth in the soil, the susceptibility of barnyard grass to pyriftalid, applied to the soil surface under water-leakage conditions, was induced principally by absorption through its absorptive parts in the soil water in the herbicide-treated layer, as similarly observed for cafenstrole (Takahashi et al 2000;Kanzaki et al 2001) and thenylchlor (Kobayashi et al 2004). Therefore, it was suggested that the concentration of pyriftalid in the soil water in the topmost layer could maintain an adequate level in order to induce residual phytotoxic activity to the lateemerged weeds.…”

“…Our previous reports demonstrated that the herbicidal activity of thenylchlor and cafenstrole, applied to the soil surface, was mainly dominated by their concentration in the soil water and that these herbicides were leached with limited downward movement in the soil under waterleakage conditions (Kobayashi et al 1994;Onoe et al 1995;Takahashi et al 2000). It was suggested that a high susceptibility of barnyard grass to these herbicides at any emergence depth in the soil was probably induced by its absorption by the underground parts in the herbicidetreated layer (Kobayashi et al 2004).…”

“…2000). It was suggested that a high susceptibility of barnyard grass to these herbicides at any emergence depth in the soil was probably induced by its absorption by the underground parts in the herbicide‐treated layer (Kobayashi et al . 2004).…”

Residual thenylchlor concentration in soil water and its phytotoxic activity in soil

“…Japonica var. Nipponbare) was used as a test plant because thenylchlor is known to cause phytotoxic activity in rice under the conditions that allow rice roots to be directly exposed to this herbicide (Kobayashi et al . 2004).…”

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).…”