Field experiments were conducted in 1994 and 1995 to determine if the sodium salt of pyrithiobac or bromoxynil applied in a low-volume, air-assist spray system controlled entireleaf morningglory, pitted morningglory, and smallflower morningglory as well as treatments applied with a conventional hydraulic fan spraying system, and to determine if herbicide rates could be reduced when using the low-volume spraying system. Pyrithiobac at 0.035 and 0.071 kg ai/ha and bromoxynil at 0.56 and 1.12 kg ai/ha were applied alone and in combination with DSMA at 1.7 kg ai/ha or MSMA at 1.7 kg ai/ha. Spraying systems were calibrated to deliver 26 L/ha and 140 L/ha for the low-volume and conventional systems, respectively. No significant differences in control were noted between low-volume and conventional spray systems when herbicides were applied at the suggested use rates of 0.071 and 1.12 kg ai/ha for pyrithiobac and bromoxynil, respectively. Morningglory control was reduced when pyrithiobac and bromoxynil were applied at one-half the suggested use rate regardless of the spraying systems. Bromoxynil alone generally controlled pitted and entireleaf morningglory better than pyrithiobac alone regardless of rate and application method. However, pyrithiobac generally provided better control of smallflower morningglory than bromoxynil. Adding MSMA or DSMA to bromoxynil and pyrithiobac increased control of both weed species.

Asulam applied POST alone and in mixtures with residual herbicides and with DSMA and MSMA was evaluated for johnsongrass control. Johnsongrass control following treatment with asulam at 3.7 kg ai ha−1 was not improved by tank mixtures with the residual herbicides atrazine, metribuzin, pendimethalin, and terbacil compared with asulam applied alone. Johnsongrass injury symptoms appeared sooner when asulam was applied in mixtures with either DSMA or MSMA, but johnsongrass control 4 wk after treatment was similar to asulam applied alone. As a result of the johnsongrass control obtained with early POST treatments of asulam applied alone, cane and sugar yields were increased by 56 and 58%, respectively, when compared with the weedy check. Additional cane and sugar yield increases were not obtained by any of the asulam mixtures because johnsongrass control was not improved. Asulam applied again in May to johnsongrass regrowth improved late-season control in two of the three studies over a single early POST application, but cane and sugar yields were not increased.