Effect of Growth Stage on the Efficacy of Postemergence Herbicides on Four Weed Species of Direct-Seeded Rice

Bhagirath Singh Chauhan,Seth Bernard Abugho

doi:10.1100/2012/123071

Bhagirath Singh Chauhan, Seth Bernard Abugho

Open Access

https://doi.org/10.1100/2012/123071

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Abstract

The efficacy of bispyribac-sodium, fenoxaprop + ethoxysulfuron, and penoxsulam + cyhalofop was evaluated against barnyardgrass, Chinese sprangletop, junglerice, and southern crabgrass when applied at four-, six-, and eight-leaf stages. When applied at the four-leaf stage, bispyribac-sodium provided greater than 97% control of barnyardgrass, junglerice, and southern crabgrass; however, it was slightly weak (74% control) on Chinese sprangletop. Irrespective of the weed species, fenoxaprop + ethoxysulfuron provided greater than 97% control when applied at the four-leaf stage. At the same leaf stage, penoxsulam + cyhalofop controlled 89 to 100% barnyardgrass, Chinese sprangletop, and junglerice and only 54% of southern crabgrass. The efficacy of herbicides was reduced when applied at the eight-leaf stage of the weeds; however, at this stage, fenoxaprop + ethoxysulfuron was effective in controlling 99% of Chinese sprangletop. The results demonstrate the importance of early herbicide application in controlling the weeds. The study identified that at the six-leaf stage of the weeds, fenoxaprop + ethoxysulfuron can effectively control Chinese sprangletop and southern crabgrass, penoxsulam + cyhalofop can effectively control Chinese sprangletop, and bispyribac-sodium can effectively control junglerice.

Highlights

Rice is an important crop in Asia, where 90% of this crop is grown and consumed
The objective of this study was to evaluate the efficacy of different postemergence herbicides on barnyardgrass, Chinese sprangletop, junglerice, and southern crabgrass when applied at their different growth stages
Delayed herbicide application after the four-leaf stage increased the number of surviving plants, and all plants of barnyardgrass survived when bispyribacsodium and penoxsulam + cyhalofop were applied at its eight-leaf stage (Table 1)

Summary

Introduction

Rice is traditionally grown by transplanting seedlings into puddled soil. Weeds are a greater problem in DSR than in transplanted rice because of the absence of the crop seedling size advantage and standing water at the time of crop emergence [2]. Barnyardgrass and junglerice are examples of “crop mimicry” as they closely resemble rice at the seedling stage. By the time these weeds can be recognized by farmers, crop yield losses may already be inevitable [5]. Rice residue of up to 4 Mg ha−1 was not able to reduce the growth of barnyardgrass [7], suggesting that the crop residue at this amount, as a mulch on the soil surface, may not provide suppression of this weed. Barnyardgrass at a density of 9 plants m−2 can reduce rice yield by more than 50% [8]

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