Seedlings of winged elm (Ulmus data Michx.), bur oak (Quercus macrocarpa Michx.), black walnut (Juglans nigra L.), eastern redcedar (Juniperus virginiana L.), and loblolly pine (Pinus taeda L.) were treated in nutrient solution with ring-labeled 14C-tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} or 14C-hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione]. Four hours later, 14C was detected in all sections of winged elm treated with 14C-tebuthiuron and 14C-hexazinone. Root absorption of the tebuthiuron label by the other species occurred in the order: loblolly pine > bur oak > black walnut = eastern redcedar. The sequence of 14C-hexazinone absorption was: loblolly pine > black walnut ≥ bur oak = eastern redcedar. Foliar accumulation of the tebuthiuron label occurred in the order: bur oak > loblolly pine > eastern redcedar = black walnut, whereas the sequence with hexazinone was loblolly pine > bur oak > black walnut = eastern redcedar. The presence of the three metabolites of hexazinone in loblolly pine suggests that it may be resistant to hexazinone as a result of its ability to degrade hexazinone rather than its ability to limit uptake.

Aerial applications of 20% tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N-dimethylurea} pellets at 2.2 kg/ha (ai) in the spring effectively controlled post oak (Quercus stellata Wangenh.), blackjack oak (Q. marilandica Muenchh.), water oak (Q. nigra L.), yaupon (Ilex vomitoria Ait.), winged elm (Ulmus alata Michx.), downy hawthorn (Crataegus mollis Scheele), gum bumelia [Bumelia lanuginosa (Michx.) Pers.], and willow baccharis (Baccharis salicina Torr. & Gray) in the Post Oak Savannah of Texas. Tree huckleberry (Vaccinium arboreum Marsh.), black hickory (Carya texana Buckl.), honeylocust (Gleditsia triachanthos L.) and cedar elm (Ulmus crassifolia Nutt.) were partially controlled by 2.2 kg/ha of tebuthiuron. Canopies of buckbrush (Symphoricarpos orbiculatus Moench), southern dewberry (Rubus trivialis Michx.), American beautyberry (Callicarpa americana L.), and persimmon (Diospyros virginiana L.) were reduced for about two growing seasons after which the woody species recovered. American beautyberry appeared to increase in abundance by the third growing season after control of the other woody species. Honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell], eastern redcedar (Juniperus virginiana L.), and Texas persimmon (Diospyros texana Scheele) were not controlled by tebuthiuron at 2.2 or 4.4 kg/ha, and saw greenbrier (Similax bona-nox L.) and peppervine [Ampelopsis arborea (L.) Koehne] apparently increased following application of tebuthiuron.