Investigating some eco-physiological aspects and chemical management of invasive weed Butomus umbellatus in paddy fields

Butomus is an aquatic weed belonging to the butomaceae family, which has invaded the paddy field ecosystem in recent years. This study was carried out in order to investigate some eco-physiological aspects and chemical management of butomus in paddy field. In the field studies; the emergence time, height, tillering, flowering, and life cycle of butomus in the paddy field ecosystem and the germination rate of bulblets in the laboratory and the effectiveness of pre-emergence and post-emergence soil-applied herbicides in pot experiments, and also foliar-applied herbicides were investigated. The results revealed that waterlogged lands are the main habitat of butomus, and the bulblets are the main reproductive organs of this weed. While puddling, about 100% bulblets are separated from the rhizomes which floated on the water and dispersed. Both rhizomes and bulblets of butomus were submergence tolerant and germinated from 15 cm or more of submergence. Flowering of butomus preceded about one week the initiation of rice panicle. Each plant produced dozens of flowering tillers taller than rice stalk, hundreds of spindle-shaped bulblets up to 25 mm long, with more than 95% emergence rate. In pre-emergence application, soil-applied herbicides including clomazone+pendimethalin, oxadiargyl, pretilachlor, pendimethalin, and thiobencarb, controlled butomus less than 65% and sulfonylureas herbicides; pyrazosulfuron, metazosulfuron, flucetosulfuron, and bensulfuron methyl provided more than 85% control of butomus. The effectiveness of sulfonylureas in the post-emergence application was around 10% lower compared with pre-emergence application. Foliar applied herbicides; penoxsulam and propanil controlled butomus 62% and 70% and its control by bispyribac sodium, penoxsulam+cyhalofop-butyl, bentazon+MCPA, and pyribenzoxim were 80, 86, 89, and 99%, respectively. Therefore, it is recommended to apply a soil-applied sulfonylurea or a foliar-applied herbicide in the paddy fields infested with butomus in addition to the specific herbicide for barnyardgrass control.