Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2005
Publication Date: 9/1/2005
Citation: Estorninos, L.E., Gealy, D.R., Gbur, E.E., Talbert, R.E., Mcclelland, M.R. 2005. Rice and red rice interference. II. Rice response to population densities of three red rice (Oryza sativa) ecotypes. Weed Science. 53:(5):683-689. doi.org/10.1614/WS-04-040R1.1. Interpretive Summary: Red rice usually grows to be much taller than domestic rice and is a major weed of rice. Field experiments were conducted at Stuttgart, AR to evaluate the growth response of a common commercial rice cultivar, Kaybonnet, to different population densities of three red rice ecotypes that differed in their potential competitiveness against rice. The tallest of the three red rice ecotypes, LA3, reduced the number of rice stems and seedheads by half and reduced grain yield by 80%. A medium height red rice, Stgstraw, reduced the number of rice stems and seedheads by 49 and 41%, respectively, and reduced grain yield by about 60%. KatyRR, the smallest of the three red rice ecotypes, was also the least competitive, reducing the rice grain yield and number of stems and seedheads by only 20 to 30%. Planting increased population densities of red rice also tended to reduce substantially the rice grain yield and number of stems and seedheads. Thus, common red rice ecotypes will be expected to reduce rice growth and yield much more dramatically than will their smaller cousins.
Technical Abstract: Red rice, which grows taller and produces more tillers than domestic rice and shatters most of its seeds early, is a major weed in many rice-growing areas of the world. Field experiments were conducted at Stuttgart, AR in 1997 and 1998 to evaluate the growth response of the Kaybonnet (KBNT) rice cultivar to various population densities of three red rice ecotypes. The red rices tested were Louisiana3 (LA3), Stuttgart strawhull (Stgstraw), and Katy red rice (KatyRR). Compared with KBNT rice alone, LA3, the tallest of the three red rice ecotypes, reduced tiller density of KBNT rice 51%, panicle density 50%, and grain yields 80%. Stgstraw, a medium height red rice, reduced KBNT rice tiller density 49%, panicle density 41%, and yield 61%. KatyRR, the shortest red rice, reduced KBNT rice tiller density 30%, panicle density 23%, and grain yield 21%. Tiller density of rice was reduced from 20 to 48% when red rice density increased from 25 to 51 plants m-2. Panicle density of rice was reduced by 13 and 72% when red rice densities were at 16 and 51 plants m-2. Yields of rice were reduced by 60 and 70% at red rice density of 25 and 51 plants m-2. These results demonstrate that even low populations of common red rice ecotypes can greatly reduce rice growth and yield and that small-statured red rice types are likely to affect rice growth less than their taller counterparts.