Field studies were conducted from 2000 through 2002 to evaluate the effects of atrazine, pendimethalin, and trifluralin applied alone or in combination followed by cultivation when weeds and grain sorghum were less than 7 cm tall (early postemergence [EPOST]) or when weeds and grain sorghum were 10 to 15 cm tall (late postemergence [LPOST]). Atrazine plus pendimethalin applied EPOST caused 9 to 14% sorghum stunting all 3 yr while atrazine plus trifluralin applied EPOST caused 1 to 4% grain sorghum stunting. When applied LPOST, atrazine plus pendimethalin or trifluralin resulted in no greater than 3% stunting. Tumble pigweed was controlled at least 99% with atrazine plus pendimethalin or trifluralin applied EPOST or LPOST, whereas Texas panicum was controlled at least 97% with atrazine plus pendimethalin or trifluralin applied EPOST, and 76 to 100% with LPOST application. Sorghum yields were reduced with atrazine plus pendimethalin applied EPOST when compared with all herbicide combinations in one of 3 yr.
Nomenclature: Atrazine; pendimethalin; trifluralin; tumble pigweed, Amaranthus albus L. #3 AMAAL; Texas panicum, Panicum texanum Buckl. # PANTE; grain sorghum, Sorghum bicolor (L.) Moench. ‘DKS 54-00’, ‘Pioneer 8313’.
Additional index words: Cultivation, crop tolerance, stunting, yield reduction.
Abbreviations: EPOST, early postemergence; LPOST, late postemergence; WAP, weeks after planting.