Abstract

The objectives of this research were to determine alternative herbicides for the control of Diplachne fusca in a greenhouse and quantify levels of yield reduction as affected by occurrence densities of Diplachne fusca in a reclaimed paddy field. An accession of D. fusca was 52–62 and 28–48% controlled even when treated with two times the recommended use rate of pyrazosulfuron+pyriminobac and methazosulfuron at two- or three-leaf stage of D. fusca, respectively. Other accessions were completely controlled by the above herbicides. The sulfonylurea-resistant D. fusca accession was controlled 100% with benzobicyclone+thiobencarb benzobicyclone+fentrazamide, fentrazamide+oxadiagyl, thoibencarb, and benzobicyclon when applied at 0 day after seeding and pyrimsulfan+ mefenacet, bensulfuron+mesotrione+pyriftalid+pretilachlor, imazosulfuron+ pyraclonil+ bromobutide, halosulfuron+indanofan+benfuresate, azimsulfuron+metamifop+ carfentrazon and bensulfuron+mefenacet+oxadiagyl when applied at 3-leaf stage, and cyhalofop-butyl and fenoxaprofop-P-ethyl when applied at 5-leaf stage. Rice yield was reduced 48 and 88% by densities of 10 and 30 plants per m2 in rice paddy fields, respectively. The rice yield loss was directly due to reduction of the number of panicle and spikelet.