Research was conducted to determine the influence of water carrier quality on grass control from sethoxydim. Water from a well near Halliday, ND, where sethoxydim failed to control grasses, contained 650 mg/L sodium and 1650 mg/L bicarbonate. Both sodium bicarbonate and sodium carbonate when included in the sethoxydim spray reduced grass species control in the greenhouse and field. Sodium carbonate in the spray generally was more antagonistic than sodium bicarbonate to sethoxydim toxicity to grasses. The antagonism from sodium bicarbonate at 6000 mg/L was overcome by diammonium sulfate or ammonium nitrate at 2.8 kg/ha or a 28% nitrogen liquid fertilizer at 9.4 L/ha in the sethoxydim spray. These compounds also overcame sodium carbonate and partly overcame the antagonism of sethoxydim by bentazon. Three commercial adjuvants for use with sethoxydim differed in their effect on wheat and oats control with sethoxydim alone or with bentazon.

Weed control research includes comparisons of herbicides, spray volumes, carriers, and application times in tall crops such as grain sorghum and corn. To accomplish this, a plot sprayer was constructed on a 15-kW tractor with 1.5-m clearance. Ten spray cans held spray mixes that were propelled by compressed air supplied by a two-cylinder single-stage compressor. Using this sprayer, two people could spray up to 66 plots per h to evaluate herbicides, growth regulators, and insecticides in tall weeds and crops using different speeds, controlled droplet applicators, rope wicks, or air-assist nozzles at low- and high-spray volumes.

The tolerance of 41- and 76-cm tall corn to sethoxydim applied with a precision postemergence-directed sprayer was evaluated in field studies in 1987 and 1988. Corn 41 cm tall at application tolerated directed sethoxydim more than corn 76 cm tall. Sethoxydim plus crop oil concentrate at 110 to 220 g/ha plus 1.3% (v/v) applied to 41-cm corn resulted in little or no injury and no corn grain yield reductions. When sethoxydim at rates exceeding 110 g/ha plus crop oil concentrate was applied to corn 76 cm tall, injury occurred which reduced corn grain yield. Good tolerance of 41-cm tall corn validates the safety and effectiveness of postemergence-directed sethoxydim when applied with precision sprayer equipment.

Picloram was applied broadcast on kleingrass pastures in the spring either as sprays or as pellets containing 2, 5, or 10% ae. The carrier in 5 and 10% pellets was inert clay, but 2% pellets were formulated with sufficient ammonium sulfate to contain 14.4% N. Dry formulations of picloram (10% ae), dicamba (5% ae), and tebuthiuron (20% ai) were compared to sprays at equal rates in a coastal bermudagrass pasture. Picloram was more effective as a spray than as pellets in two of five experiments. Few differences in weed control were observed with 2, 5, and 10% picloram pellets. Picloram applied up to 3 kg ae/ha as 2% pellets did not reduce kleingrass standing crop and up to 29 kg/ha of N as ammonium sulfate applied with or without picloram did not increase kleingrass production. None of the herbicides controlled weeds during the year following application.

The effect of ammonium sulfate on absorption of 14C-sethoxydim applied alone and with bentazon was studied in large crabgrass. Adding ammonium sulfate to 14C-sethoxydim increased 14C absorption 6-fold at 0.5 h after application but did not affect the amount of 14C absorbed 1 or 4 h after application. Applying bentazon with 14C-sethoxydim reduced 14C absorption 26%. When 14C-sethoxydim was applied with bentazon and ammonium sulfate, 14C absorption and translocation were similar to those with 14C-sethoxydim alone.

The weed control spectrum of clomazone, the influence of clomazone on the performance of other herbicides, and the performance of tank mixtures containing clomazone were evaluated from 1985 through 1987. Clomazone applied preemergence at 280 g ai/ha controlled 90 to 100% of barnyardgrass, giant foxtail, goosegrass, large crabgrass, seedling johnsongrass, prickly sida, and velvetleaf. Clomazone at reduced rates was more effective applied preemergence than preplant-incorporated for 10 of 23 weed species. Clomazone enhanced imazaquin activity on entireleaf morningglory and sicklepod in 1986. A tank mixture of clomazone, imazaquin, and metribuzin at half the labeled rates reduced soybean injury, increased soybean yield, and controlled weeds as well as the mixture at labeled rates.

Field trials were conducted in 1985, 1986, and 1987 to identify effective herbicide treatments to control mayweed chamomile in winter wheat. Dicamba at 280 g ae/ha, 2,4-D at 560 g ae/ha, and bromoxynil at 560 g ai/ha did not control 11-cm-tall or larger mayweed chamomile and inconsistently controlled smaller plants. Mayweed chamomile control generally declined with increasing weed size. DPX-M6316 at 8.8 g ai/ha and DPX-L5300 at 4.4 g ai/ha controlled 89% or more mayweed chamomile. CGA-131036 at 4.9 g ai/ha controlled 95% or more mayweed chamomile. DPX-M6316, DPX-L5300, and CGA-131036 controlled 3- to 18-cm-tall mayweed chamomile similarly.

The interaction of DPX-A7881 and clopyralid applied as tank mixtures was studied under controlled environment and field conditions on several commonly occurring weeds in canola. Control of wild mustard and wild buckwheat was not affected by mixing these herbicides. DPX-A7881 controlled wild mustard, and clopyralid controlled wild buckwheat independently of the other herbicide. However, redroot pigweed and common lambsquarters were controlled better with DPX-A7881 plus clopyralid than with either herbicide alone. The herbicides interacted in an additive to synergistic manner on redroot pigweed depending on the rate of each herbicide. DPX-A7881 and clopyralid interacted synergistically at all rates on common lambsquarters. Plant height, date of flowering, seed yield, and quality data all indicated that canola completely tolerated DPX-A7881 and clopyralid applied alone or in combination.

The growth of loblolly pine seedlings was reduced by interference from bermudagrass, tall fescue, and broomsedge. The order for treatment influence on pine seedling growth rate measurements was tall fescue > bermudagrass > broomsedge > weed free for the 2-yr study. The increase in height of seedlings for the weed free, broomsedge, bermudagrass, and tall fescue was 4.1, 2.9, 1.9, and 1.1 cm/month, respectively; and the average increase in seedling stem diameter was 1.3, 0.5, 0.4, and 0.2 mm/month, respectively.

Stipa clandestina Hackel, a native of northern Mexico, has been found in Texas and may become a serious weed problem for range managers in the southwest. Its sharply pointed leaves and tussock-forming habit make it unpalatable to cattle, but in Mexico it tends to increase with heavy grazing or disturbance. Actively growing plants can be killed by applying a foliar spray of either glyphosate or hexazinone.

Common mullein (Verbascum thapsus L. ♯3 VESTH) has an ancient relationship with man. It never has been used for food but traditionally has been respected for its mystical and medicinal powers.