In field experiments, preemergence applications of bensulide {O,O-bis(1-methylethyl)S-[2-[(phenylsulfonyl)amino] ethyl] phosphorodithioate} or DCPA (dimethyl-2,3,5,6-tetrachloro-1,4-benzenedicarboxylate) at 11.2 kg ai/ha controlled smooth crabgrass [Digitaria ischaemum (Schreb. ex Schweig.)Schreb. ex Muhl. #3 DIGIS] selectively in turf. Granular and liquid formulations of bensulide performed similarly. Napropamide [N,N-diethyl-2-(1-naphthalenyloxy)propanamide] granules when applied alone at 1.1 to 3.4 kg ai/ha were partially effective, but when combined with 5.6 kg ai/ha bensulide, controlled smooth crabgrass for the entire season. Oxadiazon {3-[2,4-dichloro-5-(1-methylethoxy)phenyl]-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one} controlled crabgrass but temporarily injured the turf. Residual control of crabgrass the year after treatment was unacceptable for all treatments.

When tank mixed with certain boadleaf-selective herbicides, fluazifop {(+)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, and fluazifop-P {(R)-2-[4-[[5-trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} were less effective in controlling two annual grasses, Texas panicum (Panicum texanum Buckl. #3 PANTE) and large crabgrass [Digitaria sanguinalis (L.) Scop. # DIGSA]. These herbicides were applied alone or were combined with the broadleaf-selective herbicides bentazon {3-(1-methylethyl)-(1H)-2,l,3-benzothiadiazin-4(3H)-one-2,2-dioxide} and/or 2,4-DB [4-(2,4-dichlorophenoxy)butanoic acid]. The herbicide combinations controlled smooth pigweed (Amaranthus hybridus L. # AMACH) and yellow nutsedge (Cyperus esculentus L. #CYPES). Increasing the rates of the grass-selective herbicides in the mixture reduced the adverse effects of 2,4-DB or bentazon.

The upper 30 cm of soil in a field infested with purple nutsedge (Cyperus rotundus L. #3 CYPRO) contained 4900 to 5100 corms and tubers/m2 6 weeks after soil rotovation and irrigation. The upper 4, 8, 12 and 16 cm of soil had 45, 79, 95 and 99%, respectively, of the corms and tubers. Lower depths of soil contained larger tubers with higher percent dry matter than the shallow depths. Of the total number of corms and tubers, 51% were from the parent population. At 6 weeks, only 15% of the total tuber and corm population were not connected to aerial parts. Tubers from the parent population had a higher fresh weight than those from the new population. Parent tubers occurred singly or in chains of up to eight tubers.

Economic performance of prescribed burning following aerial applications of tebuthiuron {N-[5-(1,1-dimethyiethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} pellets was estimated for Texas whitebrush (Aloysia gratissima [Gillies & Hook.] Troncoso # ALYLY)-dominated rangeland and for post oak (Quercus stellata Wangenh. # QUESL)-dominated mixed hardwood stands. Honey mesquite (Prosopis glandulosa Torr. # PRCJG) invasion largely negated differences in estimated beef production between treated and untreated pastures within 13 yr of controlling Texas whitebrush with tebuthiuron at 2 kg ai/ha. American beautyberry (Callicarpa americana L.) and other shrubs increased such that the woody canopy cover was 87% of the original canopy 7 yr after applying tebuthiuron at 2.2 kg/ha to a heavy cover of oaks-mixed hardwoods. Burning at 2- to 4-yr intervals after tebuthiuron applications suppressed invading shrubs and increased projected internal rates of return by about 2% for each burning, compared to herbicide application only.

Common bermudagrass [Cynodon dactylon (L.) Pers. #3 CYNDA] and johnsongrass [Sorghum halepense (L.) Pers. # SORHA] ecotypes were collected from seven locations in Texas. Ecotype responses to glyphosate [N-(phosphonomethyl)glycine], SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate), sethoxydim {2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}, fluazifop {(+)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, haloxyfop {2-[4-[[3-chloro-5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid}, and quizalofop {(+)-2-[4-[(6-chloro-2-quinoxalinyl)oxy] phenoxy] propanoic acid} were evaluated in 1982, 1983, and 1984. Johnsongrass ecotype-by-herbicide interactions and ecotype differences were detected in only one of three years. Differences were observed consistently among the herbicide treatments. Numerous bermudagrass ecotype-by-herbicide interactions were detected each year with greater diversity occurring with less-than-optimum herbicide rates. The interactions were herbicide-by-ecotype specific and were not predictable with respect to geographic site of collection.

In field studies, mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl] amino] phenyl] acetamide} was most effective as an enhancing agent for bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] and/or acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} when applied as a tank mixture compared to sequential applications. The influence of mefluidide rate on weed control was not consistent. Additives improved the control of several weed species evaluated, but mefluidide generally was only equal to petroleum oil concentrate (phytobland petroleum oil plus emulsifiers in an 83:17 ratio) as an enhancing agent for bentazon and/or acifluorfen.

In the field, eight barley (Hordeum vulgare L.) cultivars tolerated postemergence applications of AC 222,293 [a mixture of methyl 6 and 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl) m- and p-toluate] at 0.4 to 1.4 kg/ha. AC 222,293 at 0.4 kg ai/ha applied at the 1.5- to 2-leaf stage controlled wild oats (Avena fatua L. # AVEFA) 96%, whereas 0.7 kg/ha applied at the 3.5- to 4-leaf stage controlled wild oats only 93%. Sugarbeets (Beta vulgaris L.) but not alfalfa (Medicago sativa L.), corn (Zea mays L.), pinto beans (Phaseolus vulgaris L.), or sunflower (Helianthus annus L.), were injured when planted 6 to 8 months after fall applications of AC 222,293 at 0.4 to 1.1 kg/ha.

Experiments were conducted to determine the energy requirements and the most effective rotary tiller configuration for incorporating cyanazine {2-[[4-chloro-6-(ethylamino)-1,3,5-triazin-2-yl] amino]-2-methylpropanenitrile} on an 18-cm band centered on top of the previous year's corn (Zea mays L.) ridge. When the rotary tiller was operated full width at a 10-cm depth, the least cyanazine concentration was found in the center of the ridge, and the greatest concentration was found between ridges. The treatment having the greatest cyanazine concentrations in the center of the ridge and the least in the inter-row between ridges consisted of a ridge cleaner, a cyanazine application, and the rotary tiller configured to till a. 30-cm strip on the center of the ridge with a rotor enclosure. Energy requirements for operating the rotary tiller increased as the depth of operation increased, and the 10-cm depth of operation required less energy than two passes with a tandem disk.

Experiments were conducted to evaluate varietal susceptibility of azalea [Rhododendron obtusum (Lindl.) Planch] to fluazifop-P {(R)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid } and sethoxydim {2-[l-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}. Injury observed on ‘Delaware Valley White’, ‘Hinocrimson’, and ‘Poukhanense’, following broadcast applications of fluazifop-P at 1.12 kg ai/ha, ranged from 5 to 53% foliar damage. Injury symptoms observed were leaf burn, spotting, and distortion, especially in younger leaves. Sethoxydim at 2.24 kg ai/ha caused either slight or no foliar injury to the cultivars tested. Both sethoxydim and fluazifop-P caused temporary growth reduction in ‘Hershey Red’. Foliar injury or growth reduction resulting from these herbicides was temporary, with no damage evident 6 weeks after application. Although adding either crop oil concentration or a nonionic surfactant increased phytotoxicity of fluazifop-P to Hinocrimson and Poukhanense, these adjuvants were not phytotoxic to azalea cultivars when applied alone.

In 2 yr of field experiments, trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine], profluralin [N-(cyclopropylmethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)benzenamine], fluchloralin [N-(2-chloroethyl)-2,6-dinitro-N-propyl-4-(trifluoromethyl)benzenamine], ethalfluralin [N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine], and benefin [N-butyl-N-ethyl-2,6-dinitro-4-(trifluoromethyl)benzenamine] controlled white campion [Silene alba (Mill.) E.H.L. Krause.# MELAL] during the establishment of birdsfoot trefoil (Lotus corniculatus L. ‘Leo’).

Green and yellow foxtail [Setaria viridis (L.) Beauv. #3 SETVI and S. glauca (L.) Beauv. #SETLU] seed germination after 14 days were similar at 15, 20, and 25 C. However, at 10, 30, and 35 C, green foxtail seed germination was higher than that of yellow foxtail, indicating that temperature extremes influenced green foxtail seed germination less than that of yellow foxtail. Seed germination of both species was initiated at about the same time; however, green foxtail seed germinated 1 to 2 days faster than yellow foxtail at all temperatures. After 72 h in −4 bars osmotic potential solution at 25 C, green foxtail seed germination was 70% compared to 12% for yellow foxtail, suggesting that green foxtail seed may germinate more rapidly than yellow foxtail seed in soils with limited moisture.

Chlorsulfuron [2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-amino] carbonyl] benzenesulfonamide], applied at 9 to 560 g ai/ha to the soil surface, stopped shoot elongation of well established Canada thistle [Cirsium arvense (L.) Scop. #4 CIRAR] plants in the greenhouse. Root fresh weight decreased progressively as chlorsulfuron rate was increased when measured 1 month after treatment. In contrast, the number of visible root buds plus secondary shoots increased 1.9- to 2.3-fold between 9 and 67 g/ha chlorsulfuron 1 month after soil surface treatment. Despite more numerous root buds, the number of secondary shoots arising from adventitious root buds progressively decreased as chlorsulfuron rate was raised. Increases in the number of visible root buds were observed first between 3 and 4 weeks following soil application with 67 g/ha of chlorsulfuron, 2 weeks after shoot growth stopped.

A location in east Central Kansas with a history of continuous corn (Zea mays L.), EPTC (S-ethyl dipropyl carbamothioate) plus dichlormid (2,2-dichloro-N,N-di-2-propenylacetamide) plus dietholate (O,O-diethyl O-phenylphosphorothioate) application, and shattercane [Sorghum bicolor (L.) Moench. #3 SORVU] was selected for herbicide efficacy investigations. Thiocarbamate herbicides applied before planting corn failed to control shattercane in 1 of 2 years. Adding dietholate did not improve EPTC efficacy in either year. Alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] applied preplant failed to control shattercane both years. Treatments which included applications of alachlor at 2.2 kg ai/ha 7 or 10 days after preplant herbicide applications were made provided significantly better shattercane control than did preplant treatments.

A low-volume (21.5 L/ha) spinning disc (controlled droplet applicator) and a high-volume (187 L/ha) boom-nozzle applicator were compared in applying tank mixtures of the weed pathogen Colletotrichum gloeosporioides (Penz.) Sacc. f. sp.] aeschynomene (henceforth designated C.G.A.) and acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} for control of northern jointvetch [Aeschynomene virginica (L.) B.S.P. # AESVI] and hemp sesbania [Sesbania exaltata (Raf.) Rydb. ex A.W. Hill # SEBEX] in soybean [Glycine max (L.) Merr. ‘Tracy M’]. Application with a spinning disc did not increase control of either weed species over the boom-nozzle applicator. C.G.A. controlled northern jointvetch in 2 of 3 yr. Northern jointvetch control with the spinning-disc was poorer at lower rates in years of unfavorable environment. Acifluorfen at 0.56 kg ai/ha and applied with either applicator controlled hemp sesbania satisfactorily.

Sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio) propyl]-3-hydroxy-2-cyclohexen-1-one} at 0.34 kg ai/ha, fluazifop {(+)-2-[4-[[5-(trifluoromethyl)-2-pyridinyl] oxy] phenoxy] propanoic acid} at 0.13 kg ai/ha, and SC-1084 {3-hydroxy-4-[4-[[5-trifluoromethyl)-2-pyridinyl] oxy] phenoxy] pentanoic acid} at 0.28 kg ai/ha controlled ‘Tifway’ bermudagrass [Cynodon transvaalensis Burtt-Davy #3 CYNTR] x [Cynodon dactylon (L.) Pers. # CYNDA] nearly 100% when applied for 2 consecutive years. Tall fescue (Festuca arundinacea Schreb. ‘Ky 31’ # FESAR) tolerated fluazifop at 0.13 kg/ha and SC-1084 at 0.07 to 0.28 kg/ha; however, centipedegrass [Eremochloa ophiuroides (Munro) Hack, ‘common’ #ERLOP] and zoysiagrass (Zoysia japonica Steud. # ZOYJA x Zoysia tenuifolia Willd. ex trin. ‘Emerald’ #ZOYTE did not tolerate these treatments. Centipedegrass tolerated sethoxydim, zoysiagrass tolerance was intermediate, and tall fescue was injured severely. Sethoxydim at 0.22 kg/ha discolored leaves of zoysiagrass, but the turf recovered fully. Thus, bermudagrass, when mixed with either tall fescue, centipedegrass, or zoysiagrass, can be controlled selectively with herbicides applied postemergence.

Increasing the air temperature from 20 to 32 C, the water temperature from 21 to 30 C, and the wind velocity from 0 to 8 km/h increased the loss of EPTC (S-ethyl dipropyl carbamothioate) from water applied through a sprinkler by 24 to 138%. Decreasing the water temperature from 21 to 10 C decreased the loss of EPTC by 35 to 50%. Decreasing the water pressure or nozzle size by 33% or doubling the herbicide concentration did not affect the percentage of EPTC lost.

The effect of common lambsquarters (Chenopodium album L. #3 CHEAL) density on spring barley (Hordeum vulgare L. ‘Lidal’) was studied in a 2-yr field experiment near Fairbanks, AK. The data were fit to a rectangular hyperbola model. Common lambsquarters densities explained 74 to 75% of the variability in barley yield. The maximum yield loss attributable to common lambsquarters was 23% in 1982 and 36% in 1983.

Percent soil organic matter content, as determined by standard chromic acid oxidations, was highly (r = 0.89) correlated with soil humic matter content, as determined by NaOH/DTPA (diethylenetriaminepenta-acetic acid)/alcohol extraction of 201 U.S. soils. Humic matter content of the soils was equally or better correlated (r = 0.89 to 0.97) with herbicide bioactivity, as measured in field experiments, than was percent organic matter content (r = 0.87 to 0.92). Regression equations provided allow herbicide rate recommendations for 80% weed control to be calculated based on soil humic matter or soil organic matter levels.

Twenty field experiments were conducted in Oklahoma from 1983 through 1986 to evaluate the ethylthio analog of metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(ethylthio)-1,2,4-triazin-5(4H)-one] for selective control of cheat (Bromus secalinus L. #3 BROSE), downy brome (Bromus tectorum L. # BROTE), and rescuegrass (Bromus catharticus Vahl. # BROCA) in winter wheat (Triticum aestivum L.). The ethylthio analog of metribuzin applied postemergence at 1.1 kg ai/ha before the weeds tillered controlled 91 to 100% of these Bromus spp. in winter wheat. Control of tillered Bromus spp. was less consistent. As Bromus spp. control increased, wheat yields increased, and dockage decreased. The herbicide was selective on wheat over a wide range of soils, including sands. Adding surfactant to very early postemergence applications of 0.6 kg ai/ha increased cheat control but injured wheat slightly. Surfactant use had little or no effect on dockage reduction and yields.

A non-linear dose-response model was used to analyze the response of tomato (Lycopersicon esculentum Mill.) and eastern black nightshade (Solanum ptycanthum Dun. #3 SOLPT) to acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid}, fluoroglycofen {carboxymethyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate}, fomesafen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-N-(methylsulfonyl)-2-nitrobenzamide}, and lactofen {(±)-2-ethoxy-1-methyl-2-oxoethyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate}. The relative potency of these herbicides to both species was lactofen > fluoroglycofen > fomesafen > acifluorfen. Tomato was significantly more resistant to acifluorfen, fluoroglycofen, and lactofen than was eastern black nightshade, but there was no significant difference between species in response to fomesafen. At the rate required to reduce tomato weight by 10%, eastern black nightshade weight was reduced 48, 32, 20, and 5% by acifluorfen, fluoroglycofen, lactofen, and fomesafen, respectively.