Huisache is a major brush problem on native rangelands and pastures in South Texas. Although herbicide applications to foliage provide very high plant-kill levels, the same herbicides have not proven reliable when applied as broadcast ground or aerial foliar treatments. Aerial and ground broadcast herbicide foliar treatments were applied to 31 huisache sites. Soil temperature and soil moisture were measured at a depth of 30 cm at the time of herbicide application. Cumulative rainfall before herbicide application was recorded. Across all aerial treatments, plant mortality was 69% for plants shorter than 2 m versus 40% for plants taller than 2 m. Across all aerial- and ground-treated sites, plants shorter than 2 m had an average 89% mortality when cumulative 2-wk rainfall was at least 50 mm, versus 72% mortality with cumulative rainfall less than 50 mm. Average plant mortality was 84% when 4-wk cumulative rainfall was at least 76 mm, versus 71% with rainfall less than 76 mm; and 85% when, on a dry-to-wet scale of 0 to 10, soil moisture measured at least 8, versus 71% when soil moisture measured less than 8. In a separate aerial trial, plant-mortality effects of spray droplet size (417, 630, and 800 µm) and spray volume (37.4 L ha−1 and 93.5 L ha−1) were replicated and tested at a single study site in 2014. Plant mortality was lowest for the 93.5 L ha−1 and 800 µm treatment. Plant mortality rates for other treatments were similar, demonstrating a greater importance of droplet size than spray volume. Targeting huisache trees shorter than 2 m, when cumulative rainfall has reached at least 50 mm or at least 76 mm 2 or 4 wk before application, respectively, as well as maintaining spray droplet sizes no larger than 630 µm can increase herbicide efficacy with foliar broadcast applications.

Hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] was applied to honeylocust (Gleditsia triacanthos L.), honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell], huisache [Acacia farnesiana (L.) Willd.], live oak (Quercus virginiana Mill.), Macartney rose (Rosa bracteata Wendl.), post oak (Quercus stellata Wangenh.), saw greenbrier (Smilax bona-nox L.), whitebrush (Aloysia lycioides Cham.), and yaupon (Ilex vomitoria Ait.). Bromacil (5-bromo-3-sec-butyl-6-methyluracil) and tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} were used for comparison in some experiments. Hexazinone was required at the following rates to kill at least 75% of the following species: 1.1 kg/ha for live oak, 2.2 kg/ha for post oak, 4.5 kg/ha for huisache (at Bryan, Texas) and whitebrush, and 9 kg/ha for honeylocust. Hexazinone was ineffective at 9 kg/ha for control of honey mesquite, huisache (at Washington, Texas), Macartney rose, saw greenbrier, and yaupon. Tebuthiuron at 1.1 kg/ha killed 80% of the live oak, and as a subsurface spray at 4.5 kg/ha, killed huisache (at Washington, Texas). Bromacil was effective on huisache at 9 kg/ha.

Seed lots of Macartney rose (Rosa bracteata Wendl.), yaupon (Ilex vomitoria Ait.) huisache [Acacia farnesiana (L.) Willd.], and honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell] were exposed for various periods to radiofrequency (RF) dielectric heating by electromagnetic fields of 10 and 39 megahertz (MHz) at various field intensities in attempts to increase their germination. Both continuous-wave and pulse-modulated exposures were used at 39 MHz. Seed samples were preconditioned at temperatures from 24 to −43 C before exposure. Sixty-Hz a-c and d-c electrical treatments were included in some experiments. Although significant increases in germination were obtained by RF treatment of huisache and honey mesquite seed in some experiments, results with different huisache seed lots were inconsistent. The germination of Macartney rose seed was not increased, and no germination was observed in yaupon, regardless of the treatment employed.