Response of itchgrass and johnson grass to asulam/dalapon combinations

Activities of asumlam [methyl[(4-aminophenyl)sulfonyl]carbamate], dalapon (2,2-dichloropropionic acid) and asulam/dalapon combinations on itchgrass (Rottboellia exaltata L.f.) and johnson grass [Sorghum halepense (L.) Pers.] were examined. When metabolism of 14C-asulam was monitored, seven days after application, 97-100% of recovered 14C co-chromatographed with 14C-asulam. Itchgrass exhibited rapid uptake of 14C-asulam within 8 hr after application. Asumlam concentrations remained constant in the plant between 8 and 72 hr. Johnson grass plants showed a differential response to asulam and asulam/dalapon treatments. Asulam-treated johnson grass absorbed 26-34% 14C within 2 hr with no future significant increase in absorption in absorption through 72 hr. Treatment of johnson grass with asulam/dalapon enhanced 14C absorption with time. At 24 and 72 hr 14C levels were double that absorbed from treatment of asulam alone. Movement of 14C-asulam in the apoplast and symplast of both itchgrass and johnson grass was noted. The highest radiolabel accumulated in the lower leaves of itchgrass and remained in the treated leaf of johnson grass