Doses of 1-(2-methylcyclohexyl)-3-phenylurea (siduron), sprayed on seeds of several forage, turf, and weed grasses on the soil surface killed some weed grasses without injuring many desirable grasses. Seeds of tolerant grasses mixed with an excess of a dry siduron formulation and stored for 12 months germinated without injury, but crabgrass (Digitaria sanguinalis (L) Scop.) and barnyardgrass (Echinochloa crusgalli (L.)) were killed during germination. Siduron eliminated seedling weed grasses from seedling perennial turfgrasses when applied on the soil surface or incorporated in the soil just before planting. When applied as a coating on seeds of turfgrasses at planting time, siduron controlled some annual weed grasses without injurying the turfgrasses. Herbicidal action appeared to be localized mainly in the grass roots and differed from that of 1,1-dimethyl-3-phenylurea (fenuron) and isopropyl carbanilate (propham) applied at equimolar doses.

Previous research with annual weed species indicates that critical timing of weed removal begins primarily after the two-leaf stage of onion, a time when postemergence (POST) herbicides can first be applied. Volunteer potato is difficult to manage and persists in onion fields of western United States. The purpose of this research was to quantify the duration of volunteer potato interference on yield and market grade of onion as well as potato tuber production. Volunteer potato interference caused a 5% yield loss before onions reached the two-leaf stage, at two of three locations. Relative to weed-free plots, onion bulb diameter was reduced as duration of interference increased, resulting in smaller proportions of marketable bulbs. Volunteer potato produced daughter tubers shortly after emergence, which explains, in part, weed persistence despite removal of shoots with contact herbicides, cultivation, and hand-weeding in onion. Significant losses in onion yield and bulb diameter are likely given current volunteer potato management systems.

Herbicides were applied annually in March or March plus August to bermudagrass [Cynodon dactylon (L.) Pers. Tifdwarf’] putting greens for 6 yr. Bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(2-mercaptoethyl)benzenesulfonamide] delayed early spring growth of bermudagrass less than the other herbicides, but did not adversely affect turf quality during the growing season. Oxadiazon [2-tert-butyl-4(2,4-dichloro-5-isopropoxyphenyl)-Δ2-1,3,4-oxadiazolin-5-one] treatments applied twice each year severely retarded turf growth and reduced the quality and stand of bermudagrass. Napropamide [2-(α-naphthoxy)-N, N-diethylpropionamide] and prosulfalin {N-[[4-dipropylamino)-3,5-dinitrophenyl] sulfonyl]-S,S-dimethylsulfilimine} treatments reduced root growth of bermudagrass.

Shoot apices of 7-day old foxtail millet (Setaria italica (L) Beauv.) seedlings treated with 2 and 20 mg/L of dimethyltetrachloroterephthalate (DCPA) were examined under the electron microscope. Cell division is interrupted. The nucleus and nucleolus do not disintegrate and chromosomes do not differentiate. Instead, giant nuclei and giant nucleoli occupy most of the cell volume in the meristematic regions. Several nucleolar caps form on the giant nucleolus; and in the advanced stages, they separate and are encircled by a nuclear membrane to form multiple nuclei. Other organelles are also affected. Cristae and thylakoid membranes of mitochondria and chloroplasts degenerate and multiple vacuoles form. Cell walls are markedly more osmophilic after DCPA treatment. Treated cells are less turgid than controls.

Weed control during the fallow year and yields of subsequent winter wheat (Triticum aestivum L.) were lower on unsprayed plots than on plots treated with 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) at 2 lb/A or 3-amino-l,2,4-triazole (amitrole) at 1/2 lb/A plus 3-(p-chlorophenyl)-l,l-dimethylurea (monuron) at 1 lb/A. The moldboard plow gave the most effective weed control in the winter wheat-fallow rotation followed by the oneway and the sweep plow. Sweep plow tillage left the greatest amount of plant residues on the soil surface to prevent wind and water erosion, but it did not consistently destroy shallow-rooted downy brome (Bromus tectorum L.) plants. Average downy brome stands in winter wheat on fallow plots tilled with the sweep plow, oneway, and moldboard plow were 331, 114, and 16 plants per 54 sq ft, respectively. Winter wheat yields averaged for the sweep plow, oneway, and moldboard plow treatments were 17, 18, and 20 bu/A, respectively. The most feasible method of controlling weeds in a winter wheat-fallow rotation, found in this study, was oneway tillage in combination with the lower herbicide rates.

Benzadox [(benzamidooxy)acetic acid] applied at 1, 2, 3, and 4 lb/A as a postemergence treatment controlled kochia [Kochia scoparia (L.) Schrad.] selectively in sugarbeets (Beta vulgaris L.). Control increased as the rate of benzadox increased, but some kochia survived at the 4-lb/A rate. Competition from these plants reduced the yields of sugarbeet roots and sucrose. Where surviving kochia plants were removed by hand 7 weeks after emergence, all sugarbeets treated with benzadox yielded as well as the hand-weeded checks. In growth chamber studies, the activity of benzadox was increased by temperature and decreased by simulated rain which occurred within 4 hr following application. Under a temperature regime of 70 F day and 40 F night, if simulated rain was delayed for 8 hr, the control of kochia was identical to that obtained where no simulated rain followed treatment. The growth chamber studies confirmed our results with the performance of benzadox under different environmental conditions in the field.

Plant heights and seed yields of oats (Avena sativa L.), corn (Zea mays L.), and soybeans (Glycine max (L.) Merr.) were lower where these crops followed a heavy infestation of quackgrass (Agropyron repens (L.) Beauv.) than when they followed oats or fallow land. Application of ammonium nitrate (280 kg/ha) only partially corrected the adverse effect on yield of a previous quackgrass infestation. The effect of quackgrass persisted through the second growing season as measured by height and yield of wheat (Triticum aestivum L.) and compared with wheat after oats, corn, soybeans, or fallow, but the effect of nitrogen applied the first year only did not persist through the second year.

Analysis of entire barley (Hordeum vulgare ‘Moravian’) seedlings exposed to triallate [S-(2,3,3-trichloroallyl)-diisopropylthiocarbamate] vapor for 5 days after a 5-day germination period resulted in a linear rate of accumulation of triallate, while wild oat (Avena fatua L.) seedlings accumulated triallate for 1/2 to 2 days after exposure with no net accumulation thereafter. Similar accumulation patterns were shown for a similar exposure period when barley and wild oat were seeded 1.3 cm below a triallate-treated soil layer in the greenhouse. More triallate accumulated in wild oat and barley when they were planted in a triallate-treated soil layer than below. Since barley accumulated greater amounts of triallate without injury than wild oat, differential uptake of triallate was not the reason for selectivity.

Benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine) applied as a preplant incorporated treatment followed by application at the ground-cracking stage (GC) of a mixture of alachlor [(2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] plus naptalam (N-1-naphthylphthalamic acid) and dinoseb (2-sec-butyl-4,6-dinitro-phenol) significantly increased the yield of peanuts (Arachis hypogaea L. ‘Florunner’). Delaying treatment with the GC mixture for 10 days did not significantly depress peanut yields when averaged over all soils, although exceptions occurred within soil series. Substantial and consistent yield reductions occurred when the herbicide sequences terminated with five repeated applications of dinoseb, especially on the Ruston soil. Late planted peanuts often were more susceptible to intensive herbicide treatments than the early plantings. Beginning intensive sequential treatments with vernolate (S-propyl dipropylthiocarbamate) reduced yields more than when benefin initiated the sequence. Average yields of Florunner peanuts were increased significantly by the insecticide disulfoton (O,O-diethyl S[2-(ethylthio)ethyl]phosphorodithioate) on the Greenville and Ruston soil series, but not on the Dothan soil. The disulfotan x herbicide interaction was not significant. Herbicides interacted more frequently with planting date, treatment time, soil series, and year than did disulfoton.

Weed control in reduced-tillage corn (Zea mays L. ‘Pioneer 3732′) with butylate [S-ethyl bis(2-methylpropyl) carbamothioate] and EPTC (S-ethyl dipropyl carbarnothioate) was not reduced when these herbicides were applied jointly with dry or liquid fertilizer. In most cases, application with fertilizer resulted in weed control similar to that observed when the herbicide was applied in water at 285 L/ha. Butylate applied as a granular formulation also gave weed control similar to the spray at 285 L/ha. Application in 95 L/ha of water consistently resulted in reduced weed control. Corn injury was not greatly influenced by application method, and differences in corn yield appeared to be due to differences in weed control. Growth chamber bioassays indicated that both butylate and EPTC dissipated more rapidly when applied in 95 L/ha of water than the other application methods, which may explain differences in weed control observed in the field.

Proso millet (Panicum miliaceum L. ‘Turghai’, ‘M28’, and ‘Panhandle’) was planted at three or four dates from late April to late June in 1970, 1971, and 1972 on silt loam soil and in 1972 on sandy soil. A single spray application of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) at 2.24 kg/ha on half of each date plot was preemergence to the first date and preplanting to the last two or three dates of planting. Proso millet was not injured by atrazine. At each date, weed control was better on sprayed than on untreated plots. Foxtails (Setaria spp.) were the only weeds present after all plots on silt loam soil were sprayed postemergence with (2,4 dichlorophenoxy)acetic acid (2,4-D). Millet planted early produced higher yields than millet sown at normal planting dates if foxtail competition was not serious. Use of selective herbicides and spring planting offer a potential major gain in the profitability of millet production in areas where annual weed problems now relegate millet to summer planting.

Synthetic auxin herbicides are widely utilized in golf course settings for selective broadleaf weed control. Aminocyclopyrachlor (AMCP) is a newly registered pyrimidine carboxylic acid with similar chemical mode-of-action and structure to triclopyr (TRIC) and clopyralid (CLPY). Off-target injury on terrestrial plants has been documented following exposure to turfgrass clippings previously treated with TRIC and CLPY. Management practices on golf courses can distribute turfgrass clippings into water bodies; however, research has not evaluated the bioavailability of synthetic auxin residues from turfgrass clippings to aquatic and riparian plants within these environments. A bioassay study was conducted to determine the response of alligatorweed and parrotfeather to tall fescue clippings previously treated with synthetic auxin herbicides. Previously treated AMCP and TRIC + CLPY clippings were placed into growth containers mimicking a lentic system containing both alligatorweed and parrotfeather. Results indicated all herbicide treated clippings induced significant growth responses to alligatorweed and parrotfeather growth compared to a nontreated mulch and nontreated control. Alligatorweed control was greater from AMCP clippings treated 14, 7, 3, and 1 DBCC (49, 60, 90, and 80%, respectively) than comparative TRIC + CLPY clippings (33, 25, 37, and 64%, respectively) at 10 weeks after treatment (WAT). Parrotfeather control was greater from AMCP clippings (57 to 87%) than TRIC + CLPY clippings (9 to 63%) collected from all days before clipping collection (DBCC) timings when evaluated 6 WAT. At 10 WAT, greater parrotfeather control and shoot reduction was observed from AMCP than TRIC + CLPY clippings when treated 14, 7, and 3 DBCC. Based on these data, synthetic auxin residues can become bioavailable to aquatic and riparian plants within aqueous environments.

Perfluidone (1,1,1-trifluoro-N-[2-methyl-4-(phenylsulfonyl)phenyl]-methanesulfonamide) was chemically stable for 2 to 3 weeks on the surface of three Texas soils either air dry or at field capacity and at temperatures of 22 and 46 C. Perfluidone was susceptible to photodecomposition when applied to glass petri dishes and exposed to ultraviolet irradiation. Perfluidone was readily leached through neutral or slightly alkaline soils, with a tendency toward greater downward movement in soils having low clay and organic matter content. However, leaching was less in an acid loamy sand than in either neutral loamy sand or clay soils.

For effective biological control through augmentation, Bactra verutana Zeller, would have to be released against purple nutsedge (Cyperus rotundus L.) in May and June when temperatures are cooler than they are from late July through September when maximal natural populations of this biological control agent occur. Bactra larvae exposed to simulated mid-May (24/13 C) and mid-June (29/18 C) temperature regimes developed more slowly than larvae exposed to the mid-July (32/26 C) temperature regime, but nutsedge plant growth was also slower. Thus, the relative amounts of feeding injury were similar at all three regimes. Larval feeding generally increased the number of shoots slightly, but not significantly, reduced significantly the production of inflorescences, and reduced the weight of total dry matter produced between 28 and 49%.

Analysis of 3-tert-butyl-5-chloro-6-methyluracil (terbacil) in treated and untreated pairs of purple nutsedge (Cyperus rotundus L.), connected by rhizomes, indicated translocation of the herbicide. The tops and tubers of connected, untreated plants contained approximately 10% as much terbacil as did plants treated directly.

Four-year cropping sequences of continuous cotton, cotton-soybeans-soybeans-cotton, continuous soybeans, soybeans-grain sorghum-soybeans-grain sorghum, and cotton-rice-cotton-rice were treated each year with high and low levels of herbicides to control johnsongrass. High levels of herbicide were necessary to control johnsongrass in continuous cotton, cotton-soybeans-soybeans-cotton, continuous soybeans, and the soybeans-grain sorghum rotation. Johnsongrass was not eradicated, however, after 4 years of cropping sequences with high herbicide inputs. Both low and high levels of herbicide coupled with water management required for rice production controlled johnsongrass and prevented rice yield reductions.

Removing the epicuticular wax from mature pads (cladophylls) of Lindheimer pricklypear increased picloram absorption by four- to sixfold in the laboratory, while the addition of surfactant had little effect on absorption. Absorption decreased with increasing pH of the picloram solution, indicating that picloram diffused through the cuticle as the undissociated molecule. Picloram entered detached pads at the areoles more readily than through the surrounding cuticle. In the glasshouse, whole plants consisting of an old, mature pad supporting a young, growing pad absorbed picloram very slowly whether picloam was applied as a spray to old or young pads or to the soil. About 90 and 80% of the applied picloram remained on the waxy surface of old and new pads, respectively, and about 2% of the applied picloram was recovered from within the epicuticular wax after 30 days. Picloram concentrations within pads treated in the glasshouse were greater when the herbicide was applied to new pads (4.6 μg/g) than old pads (1.9 μg/g) after 30 days. More picloram was translocated basipetally from treated new pads to untreated old pads than in the opposite direction, but concentrations in untreated pads were low (<1 μg/g). Little picloram was absorbed by roots, compared to pads, and little was translocated into or out of roots. These results conflict with the view that the effectiveness of picloram for pricklypear control is attributable to extensive root uptake and acropetal transport. However, observations of plants 6 months after treatment indicated that soil applications were more effective than sprays in the glasshouse.

Control of monoecious and dioecious hydrilla [Hydrilla verticillata (L.f.) Royle # HYLLI] biotypes required a minimum 2 days of exposure to diquat (6,7-dihydrodipyrido [1,2-α:2′,1′-c] pyrazinediium ion) at a concentration of 0.25 mg/L under laboratory conditions. When treatment concentration was increased to 2.0 mg/L diquat, the minimum required contact time was reduced to 6 or 12 h depending on plant growth stage. Early growth emerging from sprouting tubers appeared to be more susceptible to diquat treatments. Herbicide uptake was linear during a 4-day exposure to 14C-diquat up to 1.0 mg/L, and the amounts of radioactivity in plant tissue varied proportionally with ambient levels of 14C-diquat in water. The lethal concentration of diquat in hydrilla tissue was estimated to be 81 μg/g plant dry weight when hydrilla was exposed to diquat at 0.25 mg/L for 2 days.

This study describes separate methods for injecting growth retardants into herbaceous and woody plants. Bean plants (Phaseolus vulgaris L. ‘Black Valentine’) were treated by injecting growth retardant solutions into the hypocotyl cavity with a syringe. The chemical was subsequently absorbed into the vascular system. Woody California privet (Ligustrum ovalifolium Hassk.) was injected by forcing chemical solution into the vascular system via a predrilled hole. Results with NAA (1-napthalene-acetic acid) and MH (1,2-dihydro-3,6-pyridazinedione) validated the methods by inhibiting growth, respectively. New growth regulators, mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl]amino]phenyl]acetamide} and dikegulac (sodium salt of 2,3: 4,6-bis-O-(1-methylethylidene-α-L-xylo-2-hexulofuranosonic acid], inhibited the growth of bean with concentrations of 60 mg/L and 480 mg/L, respectively. Sprout growth of privet was inhibited by 30 mg/L of mefluidide and by 188 mg/L dikegulac.

Spray and granular forms of isopropyl N-(3-chlorophenyl)-carbamate (CIPC, ethyl N,N-dipropylthiocarbamate (EPTC), a,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) and 2,4-bis(isopropylamino) -6-methylmercapto-s-triazine (prometryne) were incorporated preemergence to barnyardgrass Echinochloa crusgalli (1.) Beauv.) and broadleaf weeds with a rotary tiller, wheel hoe, rotary spike, or row wheel into pre-irrigated or dry soil at three locations. The locations varied in type of soil, climatic conditions, and the species of broadleaf weeds. Rotary tiller incorporation generally resulted in best weed control with both spray and granular forms under all conditions. Herbicides usually performed best in pre-irrigated soil. Sprays and granules were equal in performance at coastal and intermediate locations; granules were more effective in the desert location. Herbicidal effectiveness was influenced by method of incorporation, form of treatment, soil moisture, environmental location, and weed type.