Lj. Newsom et Dr. Shaw, EFFECTS OF RAIN-FREE INTERVALS AND HERBICIDE RATE ON SICKLEPOD (CASSIA-OBTUSIFOLIA) CONTROL AND ABSORPTION WITH AC-263,222, Weed technology, 8(3), 1994, pp. 621-624
Experiments were conducted to evaluate the effect of a 2.5-cm simulate
d rainfall 0.05, 0.25, 0.5, 1, 3, 6, and 24 h after POST applications
of AC 263,222 to sicklepod. Fresh weight reductions were directly rela
ted to increasing AC 263,222 rates and rain-free intervals. Fresh weig
ht reductions with 9, 18, 36, 54, and 72 g ai/ha AC 263,222 were 32, 4
7, 55, 59, and 67%, respectively, with the rain-free treatment. A simu
lated rainfall 0.05 h after POST application lowered fresh weight redu
ctions with 9, 18, 36, 54, and 72 g/ha AC 263,222 to 5, 7, 19, 23, and
28%, respectively, of the untreated control. As AC 263,222 rates incr
eased, a simulated rainfall shortly after POST application was less de
trimental. At 18 g/ha of AC 263,222, a 3-h rain-free interval was nece
ssary for fresh weight reductions equivalent to the rain-free control.
As the rate of AC 263,222 increased to 54 g/ha, the rain-free interva
l for fresh weight reductions equivalent to the rain-free control was
reduced to 1 h. Radiolabeled studies indicated that at 3 h after appli
cation an equivalent amount of C-14 was accumulated in the plant as co
mpared with the rain-free control. The correlation coefficients for fr
esh weight reductions and C-14 in the plant were r = 0.53, 0.75, 0.68,
0.74, and 0.70 at rates of 9, 18, 36, 54, and 72 g/ha AC 263,222, res
pectively. Nomenclature: AC 263,222, xo-1H-imidazol-2-yl]-5-methyl-3-p
yridinecarboxylic acid; sicklepod, Cassia obtusifolia L. #3 CASOB.