Biology and management of the invasive (Echinochloa oryzoides (Ard.) Fritsch) and common (Echinochloa crus-galli (L.) Beauv.) barnyardgrass in paddy field

Echinochloa oryzoides is a new specific weed of paddy fields that was first reported in Guilan in 2006 and now has infested tens of thousands of hectares of paddy fields. Characteristics of new and common species of barnyardgrass and their response to some selective rice herbicides were studied to provide a solution for their management. Results showed that panicle emergence time of new species was 11 and 21 days earlier than Hashemi rice and barnyardgrass, respectively. In addition, new one had lighter color and shorter panicle length (12.8 cm) than the common one (23 cm) and rice (27.6 cm). Seed shattering was less than 1% in new species and rice and was about 99% in barnyardgrass. Weight of 1000-seed in new species (4.5 g) was more than common species (2.5 g) and less than rice (25 g). Germination rate of one year old seeds of barnyardgrass and new barnyardgrass were 9 and 6% and it was 30 and 73% for three years seeds, respectively. The results of dose-response experiments showed that two species susceptibility to Thiobencab and Pertilachlor herbicides was similar, but the new species was more susceptible to bensulfuron-methyl. Therefore, according to the results of this study, due to the bright color and early panicle initiation, which enable easy identification of new barnyardgrass, as well as lack of seed shattering and greater susceptibility to herbicides, to manage new species, physical removing before rice harvest and also herbicide rotation especially in the fields that planted for seed production is recommended.