Competitiveness of Bensulfuron-Methyl-Susceptible and -Resistant Biotypes of Ammannia auriculata Willd. in Direct-Seeded Rice

Ammannia auriculata Willd. (eared redstem) has become one of the most troublesome weeds in paddy rice China. Resistance to bensulfuron-methyl (BSM) spread extensively this species. Greenhouse and field experiments were conducted determine how eared redstem biotype density affect competition against rice. In greenhouse experiment, five treatments tested: a BSM-susceptible at low (58 plants m−2, SL), high (288 SH), BSM-resistant (RL), (RH), control without (CK). Eared grew slowly until 15 days after sowing (DAS); however, growth accelerated 20 DAS, taller than from 55 DAS on. The SH RH associated with greater intraspecific competition: had fewer branches, capsules, less shoot dry weight per individual plant relative SL RL treatments. also caused reductions yield. 141 was reduced by 73% treatment, 98% 51% 82% all CK. At smaller plants, suggesting fitness cost herbicide resistance absence herbicide. study, densities as 5 m−2 yield 22%. A 50 70%. Overall, these findings demonstrate that is highly aggressive weed species threatens even density. However, populations are competitive. There an urgent need develop integrated management programs for weed, which may include tactics shift competitive dynamics favor Additionally, research provides theoretical basis damage level, risk evaluation, strategy cropping systems.