Five field experiments were conducted at two locations in Virginia during 1988–89 to evaluate DPX-V9360 and CGA-136872 for postemergence control of johnsongrass in field corn grown under no-till and conventional conditions. DPX-V9360 at rates of 35 (except in no-till plots), 52, and 69 g ai ha-1applied to 8-leaf johnsongrass was 88 to 98% effective in 1988. CGA-136872 at 25, 49, and 99 g ha-1was 80% effective at the highest rate. Applications of these herbicides to 6-leaf johnsongrass resulted in 69% or less control. DPX-V9360 at 35, 52, and 69 g ha-1and CGA-136872 at 20 and 40 g ha-1applied to johnsongrass up to 48 cm in height provided 77 to 97% control at 7 WAT3in an excellent stand of conventionally planted corn during 1989. Crop yields were more than doubled with herbicide treatments relative to yields in control plots. At a second location where crop damage caused by other factors resulted in a weak stand, DPX-V9360 provided 61 to 96% control compared to 29 to 56% control with CGA-136872.

Greenhouse experiments were conducted to evaluate the influence of three organosilicone surfactants (Silwet L-77®, Silwet® 408, and Sylgard® 309) and two blends of organosilicone surfactants with conventional adjuvants (Dyne-Amic® and Kinetic®) on the rainfastness of primisulfuron in velvetleaf. Four conventional adjuvants, Rigo Oil Concentrate, Agri-Dex®, methylated soybean oil, and X-77® were selected for comparison. Primisulfuron at 40 g ai/ha was applied alone or with the organosilicones, blends, or X-77 at 0.25% (v/v); the other adjuvants were tested at 1% (v/v). Simulated rainfall (1.25 cm/0.5 h) was applied at 0.25, 0.5, 1, or 2 h after treatment. Control ratings were made at 5-d intervals and shoot fresh weights were recorded 20 DAT. The organosilicone surfactants significantly increased the rainfastness of primisulfuron, even when simulated rainfall was applied at 0.25 or 0.5 h after treatment. Rigo Oil Concentrate and Kinetic also increased rainfastness when rainfall was applied 1 h after treatment. Differences among adjuvants were not as apparent when rainfall was applied 2 h after treatment. Regardless of the timing of simulated rainfall after treatment, there were significant differences between treatments and nontreated check; however, control was not acceptable in several instances.

Field experiments were conducted during 1982 to 1988 in Virginia to evaluate BAS 517, CGA 82725, clethodim, cloproxydim, fenoxaprop, fluazifop, fluazifop-P, haloxyfop, paraquat, quizalofop, SC-1084, sethoxydim, sethoxydim plus thifensulfuron, and terbacil for control of annual grasses in alfalfa. Herbicides were applied to alfalfa and grasses 2 to 30 cm in height after the first and/or second cuttings. Overall, the herbicides were highly effective in controlling fall panicum, giant foxtail, barnyardgrass, and large crabgrass. Alfalfa yields were not increased with herbicide treatments in several experiments. Only paraquat, applied later than recommended after cutting in one experiment, and sethoxydim plus thifensulfuron at one location reduced alfalfa yields.

Three seed lots each of two varieties of field corn were compared in greenhouse and field studies. Cold test germination percentages of the seed lots were as follows: 79, 85, and 93% for ‘DK656’; 77, 84, and 91% for ‘T1100’. Tank mixes of metolachlor or metolachlor with safener CGA-154281 plus atrazine or formulated metolachlor/atrazine with and without the safener were applied preemergence. Crop stand of either variety or among seed lots within a variety was not affected by herbicide treatments. In the greenhouse, fewer corn plants were injured and growth of plants was greater with herbicides with safener than herbicides without safener. Plant heights and weights at harvest from the most vigorous seed lot of DK656 were higher than those of the other two seed lots. Herbicide treatments with the safener did not cause significant injury to corn in the field. Yields of both varieties increased with herbicide treatments in one conventional planting. No significant differences in injury or yields occurred among seed lots within varieties.

SAN 582 at 1.1, 1.2, 1.3, 1.5, and 1.6 kg ai/ha; alachlor at 1.7, 2.2, and 2.8 kg/ha; and metolachlor at 1.7, 2.2, and 2.8 kg/ha were applied preemergence without and with atrazine at 1.7 kg/ha in no-till corn at two locations near Blacksburg, VA, in 1993 and 1994. SAN 582, alachlor, and metolachlor controlled TR-smooth pigweed when applied without or with atrazine, and with only a few exceptions, control was greater than 60%. The highest rate of individual herbicides was more effective than the lowest rate in most cases. Early control of TR-smooth pigweed was similar from all three herbicides, especially at higher rates, but control later in the season tended to be best with alachlor. As expected, atrazine applied alone did not control TR-smooth pigweed, and crop yields were increased with herbicide treatments compared to no treatment.