Development of control programs in soybean for reducing red rice populations in rice

Field research was conducted at three locations in 1994 and 1995 to determine the efficacy of several selective grass herbicides for red rice control and seedhead suppression in soybean. Quizalofop-P controlled red rice most consistently in differing environments. Differences between herbicides were not evident for effect on soybean yield.;Combinations of nine soybean herbicides applied PPI, PRE, POST, and/or early POST were evaluated for red rice control and seedhead suppression in three experiments at Starkville, and Shaw, MS. Red rice control was better when 2.8 kg ai/ha metolachlor, 1.4 kg ai/ha dimethenamid, 3.4 kg ai/ha alachlor, and 1.1 kg ai/ha clomazone was applied PPI as compared to PRE applications. Late POST applications of 140 g ai/ha clethodim usually increased control and seedhead suppression when following soil-applied herbicides. Imazethapyr at 70 g ai/ha and 110 g ai/ha AC 263, 222 applied POST suppressed red rice seedheads at least 87% regardless of late POST application or experiment.;Glyphosate was evaluated at three rates and application timings for red rice control and seedhead suppression in three experiments. No rate response was observed from glyphosate at 1.1 to 2.2 kg/ha. Glyphosate at any rate controlled emerged red rice but no residual control was observed. Applications to tillering red rice was more effective for control and seedhead suppression than 2-leaf or 4-leaf applications.;Field and green house studies were conducted in 1996 to determine the effect of application timing and rate of five soybean herbicides on red rice germination and young seedling vigor. Boot and bloom stage applications of 20 g ai/ha imazethapyr or 380 g/ha glyphosate, and boot stage applications of 20 g/ha quizalofop-P, reduced seedling shoot weight by at least 99% of the untreated controls. (Abstract shortened by UMI.).