The effect of rainfall on the performance of a tank mixture of desmedipham [ethyl m-hydroxycarbanilate carbanilate(ester)] and phenmedipham (methyl m-hydroxycarbanilate m-methylcarbanilate) applied postemergence to redroot pigweed (Amaranthus retroflexus L. ♯ AMARE), wild mustard (Sinapsis arvensis L. ♯ SINAR) and sunflower (Helianthus annuus L.) was evaluated in field studies. The occurrence of 1 mm of rain immediately after herbicide application significantly decreased the control of redroot pigweed and wild mustard. A rainfall quantity of 1 mm also reduced injury symptoms on sunflower. Simulating a 12.7-mm rain less than 18 h after desmedipham and phenmedipham application effectively reduced toxicity to redroot pigweed and sunflower. Toxicity to these two species increased at a lesser rate than for wild mustard as the time interval prior to rain was increased. A rain-free period of 6 h was predicted for near-maximum control of wild mustard with these herbicides.

Field experiments were conducted at two locations during 1984 and 1985 to determine how time of wild oats and wild mustard control influenced spring wheat yield and net economic return. Wheat yield and economic return were greatest when both weed species were controlled with diclofop plus bromoxynil at the 2-leaf wheat stage. Delaying the application of herbicides or controlling only wild oats with diclofop or only wild mustard with MCPA reduced wheat yield and economic benefit from the herbicide treatment. Wild oats and wild mustard competed equally for limiting growth factors in a greenhouse experiment.

Desmedipham [ethyl m-hydroxycarbanilate carbanilate(ester)] controlled wild mustard (Sinapsis arvensis L. ♯3 SINAR) and redroot pigweed (Amaranthus retroflexus L. ♯ AMARE) more effectively than phenmedipham (methyl m-hydroxycarbanilate m-methylcarbanilate). A synergistic interaction occurred with all tank-mix combinations of the two herbicides for wild mustard control, except combinations containing 0.71 kg ai/ha of desmedipham. The magnitude of the synergism decreased as the rate of desmedipham was increased and increased as the rate of phenmedipham increased. Both herbicides caused injury symptoms of leaf necrosis and height reduction to sunflowers (Helianthus annuus L.). Crop injury and sunflower heights were affected more by desmedipham than by phenmedipham. Injury effects were temporary and had no influence on sunflower yields.