Three preemergence and four postemergence herbicides were compared for control of prickly sida (Sida spinosa L.) in soybeans (Glycine max Merrill) and for level of phytotoxicity to soybeans. As a preemergence herbicide, chlorbromuron [3-(4-bromo-3-chlorophenyl)-1-methoxyl-1-methylurea] provided better control of prickly sida than did linuron [3-(3,4-dichlorophenyl)-1-methoxyl-1-methylurea] which was more consistently effective than was naptalam (N-1-naphthylphthalamic acid) plus dinoseb (2-sec-butyl-4,6-dinitrophenol). Chlorbromuron applied as a preemergence treatment caused slight crop injury. In most cases preemergence treatments followed by cultivation were effective in providing season-long control. The descending order of effectiveness for prickly sida control by the postemergence herbicides was: chlorbromuron metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] > prometryne [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine] > dinoseb. Prometryne as a postemergence treatment following a preemergence herbicide increased prickly sida control more consistently than dinoseb used as the postemergence treatment. However, prometryne caused more crop injury than did dinoseb.

Comparison of soybean yields from the weedy and weed free checks show that prickly sida caused only 9 to 14% yield losses in soybeans.

Diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], prometryn [2,4-bis(isopropylamino)-6-(methylthio)-s-triazine], and trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) were applied pre-plant in safflower (Carthamus tinctorius L. ‘AC-1′) for 6 yr at two locations. Diuron and prometryn reduced crop stands in 2 of 6 yr on the sandier soil at Mesa. Growth of sorghum [Sorghum bicolor (L.) Moench ‘Amak R-10′] in the greenhouse in soil collected 10 months after each herbicide application was reduced by 1.7 kg/ha of trifluralin in 3 of 6 yr in the Yuma silty clay loam and by both rates of trifluralin in 1 of 6 yr in the sandier soil at Mesa. Growth of barley (Hordeum vulgare L. ‘Arivat’) was not reduced in soil treated with any herbicide at either location. Herbicides did not accumulate in winter-planted safflower.

Studies were conducted on the effects of fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] on autotrophic growth (no sugar), heterotrophic growth (with sugar), and oxygen evolution and uptake and on the effects of MSMA (monosodium methanearsonate) on autotrophic growth and oxygen evolution and uptake by the unicellular green alga Chlorella pyrenoidosa Emerson strain (University of Texas). Two methods of analysis (probit and kinetic) were used to characterize the dosage-response of Chlorella to these herbicides. All measurements of Chlorella response to fluometuron were satisfactorily characterized by probit analysis, but only autotrophic cell number was adequately characterized by kinetic analysis. The fluometuron concentrations giving 50% inhibition on the probit plot were as follows: autotrophic cell number, 2.4 × 10−6M; chlorophyll at 400 nm, 3.3 × 10−6M; heterotrophic cell number, 2.4 × 10−6M; oxygen evolution, 20 × 10−6 M. The response of the alga to MSMA was stimulatory instead of inhibitory. Since this stimulation did not consistently range between 10 and 90% of the control, it was not possible to characterize the MSMA dosage-Chlorella response using either type of analysis.

The use of 2,4–dichlorophenoxyacetic acid (2, 4–D) for weed control in irrigated regions, especially on ditch banks, provides possibilities of contaminated irrigation water. A series of investigations has been conducted in the field to determine the response of certain crop plants to applications of 2,4–D in irrigation water, particularly at rates totaling herbicidal dosages. The first investigation dealt with Red Mexican beans and the results were published in 1954. This report deals with sugar beets, a root-type of crop plant.

Multiple applications of several preemergence herbicides were evaluated for weed control and for phytotoxicity to gladiolus (Gladiolus X hortulanus L.) grown from cormels in 1984 and 1985. Oryzalin [4-(dipropylamino)-3,5-dinitrobenzenesulfonamide] consistently provided acceptable control of southern crabgrass [Digitaria ciliaris (Retz.) Koel. # DIGSP], goosegrass [Eleusine indica (L.) Gaertn. # ELEIN], and smooth pigweed (Amaranthus hybridus L. # AMACH) and had minimal effect on gladiolus plant growth even after four applications. Pronamide [3,5-dichloro (N-1,1-dimethyl-2-propynyl)benzamide], alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide], and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] provided erratic weed control and reduced yields of gladiolus corms.

Studies conducted near Bernardo, New Mexico, from 1962 to 1964 involved the influence of environment on weekly shoot growth and carbohydrate storage in roots and stems of undisturbed saltcedar (Tamarix pentandra Pall.) and of regrowth (plants regrown from having been mowed the previous winter). Environmental variables were air and soil temperatures, relative humidity, wind, solar radiation, barometric pressure, evaporation from a free-water surface, depth to water table, and water quality. No variable or combination of variables could be used to predict accurately the maximum shoot growth period or the minimum carbohydrate storage. An analysis of the individual weekly growth patterns of plants showed considerable week-to-week variation in the rate of growth. Wide variations in total carbohydrate storage in roots and stems within weeks also were evident, and probably reflected the variation in growth.

Structural studies were conducted to evaluate the effects of napropamide on the growth and development of corn roots. At 1.0 and 10.0 μM napropamide, root growth was inhibited severely within 3 days of seed germination. Root diameter within 1 mm of the root apex doubled and numerous lateral root primordia were observed within 10 mm of the meristem tip in treated roots. The number of cortical parenchyma cell files, xylem vessel, and phloem sieve tube strands also significantly increased. Average cortical cell size did not change, regardless of the treatment. A lateral expansion of the meristematic region of the root coincided with a slight reduction in meristem length but resulted in an overall increase in meristem volume. However, enlargement of the meristem occurred despite a reduction in the number of mitotic figures in the root meristem. Treatment of excised root tips for 24 h with 20 μM napropamide reduced the number of mitotic figures 84%.

A nonphytotoxic paraffinic oil at 2.5, 5, and 10% (v/v) or a blended alkylaryl sulfonate surfactant at 0.5, 1, and 2% (v/v) did not enhance the activity of propanil (3′,4′-dichloropropionanilide) at 1.7, 3.4, and 6.7 kg/ha applied as a foliage spray in aqueous systems on barnyardgrass [Echinochloa crus-galli (L.) Beauv.] or rice (Oryza sativa L. ‘Starbonnet’). Time and rate of applying propanil affected control of barnyardgrass. Barnyardgrass control and rice yield were best with treatments of 3.4 or 6.7 kg/ha of propanil to four-leaf grass plants. Propanil at 6.7 kg/ha controlled tillering and jointing barnyardgrass well enough to increase grain yields over those of untreated rice.

The newly developed herbicide buthidazole {3-[5-(1,1-dimethylethyl)-1,3,4-thiadizol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone} was studied with respect to its interaction with soils and homoionic clay minerals and its response to irradiation with ultraviolet light. Results showed that it could enter the interlamellar spaces of swelling clays such as smectite. Isothermic adsorption studies indicated that Cu+2-smectite adsorbed more buthidazole than Cu+2-kaolinite. The Cu+2-clay adsorption isotherm fitted the Langmuir model. The effect of exchangeable cations on adsorption was not significant in soils of high organic matter content. Bioassay studies indicated that buthidazole's phytotoxicity was not decreased in either clays or in organic soils. Infrared spectroscopic studies showed the coordination of buthidazole with Cu+2 through C=O Cu interaction with buthidazole resulted in a ligand-to-metal ratio to 1:1. Protonation of buthidazole occurred in Al+3-and H+-smectite. The herbicide was labile to UV-light irradiation at 254 nm but not at 366 nm. The photoconversion indicated a first-order reaction. The photolytic product(s) included the –N=C=O structure. Copper(II) ions, which form complexes, retarded photolysis of buthidazole in UV-light, but the Ca+2 ion, which is unable to form complexes, did not.

On rich alluvial soils where corn is the principal crop, Johnsongrass is the most serious perennial weed in Ohio at least as far north as the 40th parallel, and it has spread rapidly north of that area, even into southeastern Michigan. Many people still credit the statements of Piper (3), Vinall (6), and Bennett (1) that Johnsongrass behaves as an annual north of the 38th parallel. Pammel and King (2), to be sure, reported Johnsongrass as a perennial weed in southwestern Iowa in 1919 and the junior author's experience with it as a weed in Ohio, from the 40th parellel south, began in 1918. At Columbus these infestations have lived through winters in which the temperature was below 0° F for prolonged periods and the ground was frozen to a depth of 6 to 8 inches. There seems to be no hope for the eradication of Johnsongrass by mere freezing.

We developed a technique to measure the projected leaf area of plants any time during the day or night. “Projected leaf area” is the leaf area seen from directly above, and is the area most likely to intercept herbicide spray from an over-the-top application. The technique involves photographing a plant and a reference square of known area from directly overhead using a light-tight box containing a flash unit. Negative images thus obtained are reflected (by means of a slide projector and mirror) onto filter paper lying on a glass stage. The projected leaf area is determined by planimetry of the negative image of the leaves and the reference square. The projected leaf area can be compared to the actual total leaf area after one determines the latter with a conventional area meter.

Experiments were conducted in environmental chambers to the evaluate effects of photoperiod and temperature on Florida betony growth and development. Plants were exposed to two photoperiods, short day (9 h) and long day (9 + 3 h night interruption), and three day/night temperature regimes, 18/14, 22/18, and 26/22 C. After 10 wk of growth, shoot length and weight were 3.4 and 3.5 times greater, respectively, in the long-day photoperiod and with the 26 and 22 than with the 22 and 18 C day and night temperature regime, respectively. Shoot number, however, was greatest in the short-day photoperiod and at a lower temperature of 22/18 C. Shoot number in long day 22/18 C and 26/22 C environments increased asymptotically. No difference in root weight was observed between long- and short-day environments, but root weight increased with increasing temperature. Flowering and tuber production only occurred in long-day environments, with greater production of both at higher temperatures. Results provide a general framework for understanding Florida betony growth and development characteristics in the field and provide insights that should be considered in developing control strategies.

Sugarcane (Saccharum interspecific hybrids) grown without cultivation but maintained relatively weed-free with herbicides and hand hoeing, produced yields of sugarcane/ha and sugar/ha in the plant, first-ratoon, and second-ratoon crops that were 100%, 95%, and 88%, respectively, of the yield of sugarcane cultivated two to four times annually. Standard cultural practice involves at least two cultivations, namely, the off-barring and the fertilizational cultivations. Additional cultivations did not substantially increase yield. When sugarcane yield was affected either by cultivation or herbicide treatment, stalk population rather than stalk weight was affected the most. Johnsongrass [Sorghum halepense (L.) Pers.] and annual weeds were controlled effectively in both cultivated and non-cultivated sugarcane with broadcast, preemergence application of fenac [(2,3,6-trichlorophenyl)acetic acid] at 5 kg/ha or terbacil (3-tert-butyl-5-chloro-6-methyluracil) at 1.8 kg/ha. Purple nutsedge (Cyperus rotundus L.), however, was controlled only with a combination of fenac or terbacil and periodic cultivation.

Greenhouse studies suggested that dog mustard was less competitive than wheat, but of similar competitiveness to flax. In field studies, dog mustard growth and development were markedly affected by crop competition. Competition from flax and wheat reduced dog mustard leaf area, shoot dry weight, plant height, and seed production compared with the weed grown on summer-fallow. Dog mustard was a prolific seed producer when grown in the absence of interspecific competition. On summer-fallow, dog mustard produced as many as 79,100 seeds plant−1 when moisture was not a limiting factor. However, average seed production was 19,400 and 8000 seeds plant−1 in 1994 and 1995, respectively.

Swainsona salsula is an unpalatable legume of Asiatic origin which spreads by seed and lateral roots and has become a problem in some poorly drained, marshy, or saline areas of several western states. Its growth characteristics indicate a high potential for establishment along stream banks, irrigation canals, wasteways, pastures, and meadows with high water tables and other poorly drained areas. Its aggressiveness results in its dominance on such areas. 2-(2,4,5-trichlorophenoxy)propionic acid (silvex), 2,4-dichlorophenoxyacetic acid, (2,4-D), or 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) applied at 2 lb/A for 2 or more years in succession controlled swainsonpea satisfactorily on cropped land. 2,3,6-trichlorobenzoic acid (2,3,6-TBA) was also effective.

Crabgrass, the universal lawn weed, has been the object of much research in the past few years. Lawn owners, cotton and vegetable growers, and golf course keepers have long been fighting this pest. Today, chemical eradication is rapidly displacing costly, difficult, and often ineffective mechanical control methods.

Colonial bentgrass (Agrostis tenuis Sibth) and creeping bentgrass (Agrostis palustris Huds) exhibited the most tolerance to 1/2, 1, 1 1/2, and 3 lb/A of 2-(2,4,5-trichlorophenoxy)propionic acid (silvex) when grown under cool temperatures, a long photoperiod, and a low pH medium. Injury from treatments was slight to moderate when applied from early to mid-spring, severe when made from late spring to early summer, and very severe when made from late summer to early fall. Silvex appeared to cause the most injury at the 1 and 1 1/2 lb/A rates. Injury was much less from the lower rate of 1/2 lb/A. Root fructosan concentrations decreased with increasing rates under cool temperatures and increased with increasing rates under high temperatures. Bentgrass appeared to tolerate silvex treatments better under low available moisture conditions than under high moisture levels.

In 1954 the authors reported studies involving the application of sodium 2,2–dichloropropionate (sodium salt of dalapon) to wild oats (Avena fatua) and concluded that treatment in the boot stage showed no promise in controlling viable seed production in wild oats. However, a lag in germination in seed from treated plants was noted in some instances (1). When seeds from these plants were planted in the greenhouse, many seedlings reached the coleoptile stage only, and failed to develop further (2).

Control of big sagebrush (Artemisia tridentata Nutt.) with fire, chemicals, or mechanical means has long been recognized as an effective method for rangeland improvement. If this sagebrush is killed or weakened by some method of control, excellent stands of grass may be obtained if all conditions are favorable. Bohmont states that as the percentage of sagebrush control increases, the grass and grasslike species also increase.

Canada thistle [Cirsium arvense (L.) Scop.] infestations were treated with 3-(p-chlorophenyl)-1,1-dimethylurea (monuron) at 10 rates ranging from 5 to 160 lb/A. Depths to which monuron leached were determined annually by bioassays with flax, peas and wheat. Toxicity at all rates continued for 3 years. The low sand, high clay, and high organic matter contents of this soil combined with cool or dry climatic conditions inhibited leaching and prolonged the toxicity of monuron.