Response of Digitaria ciliaris and Cyperus spp. Populations to s-metolachlor and alachlor Herbicides in Korea

Abstract

This study examined how Digitaria ciliaris and Cyperus spp. populations in Korea respond to and develop herbicide resistance to s-metolachlor and alachlor. Seeds of D. ciliaris and Cyperus spp. were collected from 69 and 51 sites respectively, and a whole-plant doseresponse experiment was conducted in an experimental greenhouse. Nonlinear curve fit analysis elucidated GR50 values (the dose resulting in a 50% reduction in fresh weight) of D. ciliaris ranging from 38.3–124.6 g a.i. ha-1 for s-metolachlor and 23.6–38.2 g a.i. ha-1 for alachlor, resulting in a baseline sensitivity index (BSI) of 3.25 for s-metolachlor and 1.61 for alachlor. In the dose-response test with Cyperus spp., GR50 values ranged from 41.9–98.4 g a.i. ha-1 for s-metolachlor and 25.2–33.7 g a.i. ha-1 for alachlor, resulting in BSI values of 2.34 for s-metolachlor and 1.33 for alachlor. This study found no evidence of s-metolachlor and alachlor herbicide resistance in D. ciliaris and Cyperus spp. populations in Korea. However, regular monitoring and baseline sensitivity studies should be conducted to detect the potential evolution of herbicide-resistant weed populations.