Response of Itchgrass and Johnsongrass to Asulam/Dalapon Combinations (Sugarcane, Absorption, Translocation).

A series of studies were conducted from 1983-1985 under greenhouse, field, and laboratory conditions. Activities of asulam methyl (4-aminophenyl)sulfonyl carbamate , dalapon (2,2-dichloropropionic acid) and asulam/dalapon combinations on itchgrass (Rottboellia exaltata L.f.) and johnsongrass Sorghum halepense (L.) Pers. were examined. Combinations consisted of tank mixes and sequential applications. Visual evaluations were taken 3 and 6 weeks after treatment (WAT) in 1983 and 4 and 8 WAT in 1984. Twelve WAT plant height, stem number, seedhead number and biomass were measured. Visual evaluation results paralleled quantitative measurements. Itchgrass and johnsongrass control equivalent to or greater than control obtained with 3.7 kg/ha asulam was observed with a tank mix of 2.2 kg/ha asulam plus 3.4 or 4.5 kg/ha dalapon. Sequential treatments which consisted of initial dalapon application followed 0, 1, 2, or 3 weeks later with asulam provided equivalent control to tank mixes. When metabolism of (\u2714)C-asulam was monitored, seven days after application, 97-100% of recovered (\u2714)C co-chromatographed with (\u2714)C-asulam. Itchgrass exhibited rapid uptake of (\u2714)C-asulam within 8 hr after application. Asulam concentrations remained constant in the plant between 8 and 72 hr. Johnsongrass plants showed a differential response to asulam and asulam/dalapon treatments. Asulam-treated johnsongrass absorbed 26-34% (\u2714)C (of total recovered) within 2 hr with no future significant increase in absorption through 72 hr. Treatment of johnsongrass with asulam/dalapon enhanced (\u2714)C absorption with time. At 24 and 72 hr (\u2714)C levels were double that absorbed from treatment of asulam alone. Movement of (\u2714)C-asulam in the apoplast and symplast of both itchgrass and johnsongrass was noted. The highest radiolabel accumulated in the lower leaves of itchgrass and remained in the treated leaf of johnsongrass