Field experiments were conducted in north-central Oklahoma to evaluate the effects of MON 37500 at 35, 70, and 140 g ai/ha applied to wheat on rotational crops seeded no-till 16 to 29 mo after treatment (MAT). Wheat yields were not reduced by MON 37500 at site 1 but at site 2 were decreased 6, 11, and 24% by 35, 70, and 140 g/ha, respectively. Wheat yield reductions at site 2 were attributed to late seeding, small wheat growth stage, and cool, wet weather during the month after application. Corn and soybean seeded approximately 16 MAT were not visibly injured by residual MON 37500 at any rate at either site. At site 1 grain sorghum seeded 17 MAT was visibly injured by residual MON 37500 applied at 70 and 140 g/ha (soil pH value 6.4), and grain yield was reduced 58% by residual MON 37500 applied at 140 g/ha. Grain sorghum seeded 17 MAT was not visibly injured at site 2 (soil pH value 5.0), and that seeded 29 MAT was not injured at either site. Sunflower seeded 17 MAT at site 1 was visibly injured by residual MON 37500 at 140 g/ha, and yield was reduced 17% but at site 2 was not affected by MON 37500. Sunflower seeded 29 MAT was not injured at either site.

Nomenclature: MON 37500, 1-(4,6-dimethoxypyrimidin-2-yl)-3-(2-ethanesulfonyl-imidazo[1,2-a]pyridine-3-yl)sulfonylurea; corn, Zea mays L. ‘Dekalb 566 RR’; grain sorghum, Sorghum bicolor (L.) Moench ‘Dekalb 36’, ‘Pioneer 8500’; soybean, Glycine max L. ‘Asgrow 3701 RR’; sunflower, Helianthus annuus L. ‘Dekalb 3872’, ‘Pioneer 6451’; winter wheat, Triticum aestivum L. ‘2163’, ‘Tonkawa’.

Additional index words: Crop injury, precipitation, soil pH, sulfosulfuron.

Abbreviations: MAT, months after treatment.