Management of grass levees in Seto Inland Sea area by mowing plus bispyribac herbicide

Abstract

Grass levees in the Seto Inland Sea region, composed mainly of Zoysia japonica Steud. cultivar ‘Asagake’, are mown three times a year, in May, July and September. We studied replacing the July mowing with a single application of a herbicide, bispyribac sodium salt solution. In 2016, there was no significant difference in the multiplied dominance ratio of grass leeves (m³/m²), [plant community height (m)×coverage (m²/m²)] in September between herbicide application from early June to late July and the conventional July grass cutting. In 2017, the community height was almost the same between herbicide application from late June to late July and the conventional July grass cutting. However, the multiplied dominance ratio (including the control) increased to 2.4 times the 2016 value owing to the dominance of cogongrass [Imperata cylindrica (L.) P. Beauv.], and the coverage of Z. japonica declined. The results show that substituting herbicide for mowing in July is possible when I. cylindrica is sparse during spraying.