Dinitramine (N4,N4-diethyl-α,α,α-trifluoro-3,5-dinitrotoluene-2,4-diamine) applied at 0.37 kg/ha controlled black nightshade (Solanum nigrum L.) better than did trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 0.56 kg/ha. Dinitramine applied at 0.37 kg/ha was equal to 0.56 kg/ha of trifluralin for control of green foxtail [Setaria viridis (L.) Beauv.], yellow foxtail [Setaria glauca (L.) Beauv.], and redroot pigweed (Amaranthus retroflexus L.). Dinitramine produced more root aberrations in sugarbeets (Beta vulgaris L. ‘Mono Hy D2′) than did trifluralin when sprayed on nonexposed or exposed hypotcotyledonary tissues of seedlings. When soil surrounded most of the hypocotyls at the time of application, 0.56 kg/ha of dinitramine affected 57 to 87% of the roots, whereas the same rate of trifluralin affected 1 to 8% of the roots. When the hypocotyls were exposed at the time of application, 100% of the roots were affected by dinitramine compared to 25% of all roots treated with trifluralin. Dinitramine applied at 0.37, 0.42, and 0.56 kg/ha lowered the quality and yield of sugarbeet roots, with the highest rate significantly reducing percentage purity, percentage sucrose, and recoverable sucrose. Trifluralin did not affect these parameters.

The principle of the variable dosage or logarithmic sprayer was described first in 1955. Since that time at least two sprayers utilizing this principle have appeared. Certain limitations were, however, encountered in adapting these sprayers for small plot testing under field conditions.

Poisonous plants and noxious weeds are often chemically examined to determine concentrations of secondary metabolites which are responsible for their toxic or biological activity. This study examined sample size requirements and sample methods necessary to quantify accurately the concentrations of individual and total toxic alkaloids in two tall larkspur populations. A high performance liquid chromatography analytical method was utilized to determine toxic alkaloid concentrations in all leaves from three individual plant stems and leaves from the remaining stems (remainder) from each of 50 plants in each population. To obtain high precision in quantifying toxic alkaloids in the larkspur populations (within 2.5 to 5% of the population mean, 0.95 confidence), very large numbers of samples (>50–200) were required. However, lower precision (within 10% of the population mean, 0.90–0.95 confidence) required only 20 samples. Similarly, testing parameters relating to toxin concentration in tall larkspur populations within 5 or 10% of the population mean also required hundreds of samples at power levels of 0.95 and α-levels of 0.05. Relaxing power and α-level requirements to 0.80 and 0.1 respectively, reduced sample size to about 30. The means obtained by four different sampling methods were similar (P>0.05). Alkaloid concentrations in leaf samples from single stems were highly correlated to whole-plant leaf (remainder) samples (r2≥0.76), indicating that harvesting leaves from single stems provided representative samples of the entire plant. The results indicate the difficulty in obtaining accurate information about toxins in poisonous plant populations for risk assessment by livestock producers or extension agents and demonstrate the necessity for efficient analytical methodology. Researchers evaluating concentrations of plant compounds in other weeds or toxic plants should consider variability, sampling procedure, and sample size before experiments begin.

The effect of PBA, dalapon and amitrole applications on the osmotic pressure, electrical conductivity and pH of quackgrass rhizome sap and the total nitrogen and hygroscopic capacity of dried rhizomes, from May 17 through October 15, are reported. Characteristic seasonal curves were developed for all five specific factors studied. The herbicide treatments accentuated the variation in some of these factors but did not appreciably modify the seasonal curves.

A successful weed control program, whether it be Federal, State or County is involved with research, education and regulation.

Had laws been enacted and properly enforced in all states thirty or forty years ago to prohibit the introduction of noxious weeds the weed problems of today would not be so serious.

Spot-treatments of young cotton with 2,2–dichloropropionic acid, simulating control of clumps of perennial grass, resulting in 10 to 25% reductions in cotton stands, did not cause proportional reductions in yields of seed cotton. Increased growth of cotton plants adjacent to skips compensated for reduced stands. The treatments did not affect boll components or fiber properties of cotton.

The pre- and postemergence herbicidal activities and specifications of 16 substituted toluidines on eight species were determined at two application rates. CF3-analogs were more active as preemergence treatments, and CH3-analogs were more active as postemergence treatments. Preemergence toxicity to crops was decreased in the CF3 and CH3 series when the N-substituents contained more than six carbons.

A number of investigators have tested 2,4–D (2,4–dichlorophenoxyacetic acid) for the control of weeds in asparagus. Several workers (1, 3, 4, 6) have suggested the use of 2,4–D at rates varying from one to three pounds acid equivalent per acre as a pre-emergence treatment after disking in the spring and again after disking at the end of the cutting season. Warren and Hernandez (5) applied 2,4–D at the rate of four pounds per acre on April 28 just after the asparagus bed was disked. The yield and appearance of the asparagus spears was not affected by the treatment. According to Ahlgren et al. (1), pre-emergence application of 2,4–D caused injury to the first emerging spears in some cases, but caused little permanent damage. These and other investigators found asparagus plants susceptible to foliage applications of 2,4–D and warned against spraying the fern.

The purpose here was to study fundamental aspects of polyphenoloxidase in dormant tubers.

Fenac [(2,3,6-trichlorophenyl)acetic acid] and 4-amino-3,5,6-trichloropicolinic acid (picloram) at 28 and 2.2 kg/ha, respectively, controlled woollyleaf bursage (Franseria tomentosa Gray) for 3 years in noncropped areas. Effective control of woollyleaf bursage was obtained when treated at the bud stage or earlier with an ester formulation of (2,4-di= chlorophenoxy)acetic acid (2,4-D) at 2.2 kg/ha or 3-amino-s-triazole (amitrole) at 4.5 kg/ha in an oil-water emulsion carrier or 3,6-dichloro-o-anisic acid (dicamba) at 2.2 kg/ha in a water carrier with 0.5% surfactant. Picloram, at 0.44 kg/ha or more, controlled woollyleaf bursage at any time of application.

The shoots of naturally established specimens of turkey oak (Quercus laevis Walt.) and red maple (Acer rubrum L.) were treated under conditions of approaching dormancy. Aqueous sprays of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) were applied as foliar treatments to the point of run-off at 2-week intervals beginning September 13 and continuing until three applications had been made for turkey oak and five had been made for red maple. Three experiments were conducted for turkey oak and two for red maple. Application rates were 2, 4, 8, and 16 lb of 2,4,5-T aehg of spray solution except that the 16-1b rate was deleted for turkey oak. Ester and amine derivatives were evaluated. Responses measured 9, 12, and 24 months after initiation of the experiments were percent control of original shoots, percent control of new shoots, shoot height, and number of live stems/plant. The average estimated control of original shoots of turkey oak and red maple increased from 42 to 54% as the application date was advanced from September 13 to October 11. The average height of the plants treated September 13 considering all evaluation dates was 3.4 ft compared to 2.6 ft for treatment made 4 weeks later. The results suggest two seasonal peaks in the response of some woody plants to foliar treatments of 2,4,5-T and that herbicidal effectiveness can be enhanced by application at the onset of senescence and dormancy.

Treatments were applied to heavily infested johnsongrass [Sorghum halepense (L.) Pers.] in the field for 3 years. Half of each treated plot was cultivated 5 weeks after planting soybeans [Glycine max (L.) Merr.]. Dalapon (2,2-dichloropropionic acid) applied to johnsongrass foliage 7 to 10 days before plowing plus either of the following three preplant incorporated herbicides, trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), nitralin [4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline], or vernolate (S-propyl dipropylthiocarbamate), gave 85, 68, and 82% johnsongrass control, respectively, at the end of a 3 year study. The preemergence incorporated herbicides applied following plowing and two diskings resulted in poor (35 to 50%) johnsongrass control with significant yield reductions in 2 of the 3 years. When the preemergence incorporated herbicides were applied following two diskings and eight rototillings, johnsongrass control was 62% after 3 years which was significantly less than the 79% control resulting from dalapon plus preemergence herbicides. Cultivation 5 weeks after planting soybeans increased johnsongrass control 22, 35, and 36% and soybean yields 439, 370, and 320 kg/ha in 1969, 1970, and 1971, respectively, over comparable plots without cultivation.

The influence of manure and herbicide applications on weed-free fieldbeans (Phaseolus vulgaris L.) and root rot of fieldbeans was studied during 1978 and 1979 at Scottsbluff, Nebraska. Rates of cattle feedlot manure used were 0, 30000, 56000, 112000, or 168000 kg/ha. Preplant herbicide treatments used were alachlor [2-chloro-2′6′-diethyl-N-(methoxymethyl)acetanilide] at 3.4 kg/ha, EPTC (S-ethyl dipropylthiocarbamate) at 3.4 kg/ha, EPTC + trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) at 2.2 + 0.6 kg/ha, or dinoseb (2-sec-butyl-4,6-dinitrophenol) at 6.7 kg/ha. Manure rates of 56000 kg/ha or higher reduced fieldbean yields both years, but did not increase electrical conductivity or soil exchangeable sodium enough to explain these yield reductions. In 1978, but not in 1979, height and yield of weed-free fieldbeans were reduced by EPTC, EPTC + trifluralin, and alachlor treatments. A significant interaction between manure and herbicide treatments was not detected and none of the treatments increased the severity of root rot in either year.

The effects of chloride salts of potassium, sodium, ammonium, and lithium and abscisic acid (ABA) on the translocation of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] in bean (Phaseolus vulgaris L. Var. Stringless Green-pod) seedlings were determined. 14C-labeled 2,4,5-T was injected in the stem tissue at the cotyledonary node in a 1-μl volume along with ABA. The salts were added to the nutrient solution at 20 mM concentrations at the time of 2,4,5-T treatment. Sodium chloride inhibited 2,4,5-T accumulation in the upper portion of the plant; and except for LiCl, the salts tended to increase accumulation in the nutrient solution. LiCl increased 2,4,5-T accumulation in the young shoots and primary leaves and decreased accumulation in the roots and nutrient solution. The effects of ABA on 2,4,5-T translocation were similar to the effects of NaCl but were more pronounced. ABA caused large decreases in 2,4,5-T translocation to the young shoots and primary leaves and increased accumulation in the nutrient solution.

Research studies evaluated effects of the auxin transport inhibitor, diflufenzopyr, on the biokinetics and efficacy of aminocyclopyrachlor-methyl ester (AMCP-ME) applications to black nightshade and large crabgrass. Absorption, translocation, and metabolism of 14C-AMCP-ME was quantified with and without diflufenzopyr (35 g ai ha−1). Diflufenzopyr had minimal effects on translocation of radioactivity in either species. Accumulation of radioactivity in aboveground plant sections of black nightshade was greater than or equal to that in large crabgrass by 72 h after treatment (HAT). In both species, metabolism of 14C-AMCP-ME was rapid, as 60 to 78% of the extracted radioactivity was the free acid metabolite 8 HAT. In the greenhouse, black nightshade and large crabgrass were treated with AMCP-ME (9, 18, and 35 g ai ha−1) alone and in combination with diflufenzopyr (35 g ha−1). Mixtures of AMCP-ME plus diflufenzopyr did not increase large crabgrass control compared with AMCP-ME alone at any time. Diflufenzopyr (35 g ha−1) increased black nightshade control with AMCP-ME (18 and 35 g ha−1) 7 d after treatment (DAT). However, this increase in control was not observed 14 or 28 DAT. All treatments containing AMCP-ME controlled large crabgrass 70 to 79% 28 DAT compared with > 93% for black nightshade at the same time point.

In reviewing weed control literature, papers are frequently encountered in which the data have been presented without statistical evaluation. It is important for research workers in the herbicide field to be able to estimate the validity of their comparison just as it is for the workers engaged in fertilizer studies or any other phase of field research. Arithmetic means presented alone in a graph or in a table are extremely difficult to evaluate. Even though the author of a paper may have confidence in the significance of his data, it is difficult for the reader of a research report to evaluate the conclusions if an estimate of the experimental error is not presented. This may seem to place undue emphasis on statistical analysis itself. Yet in the relatively new field of weed control, few workers have had sufficient experience to judge the significance of differences of varying degree.

Yaupon (Ilex vomitoria Ait. ♯ ILEVO) in the Post Oak Savannah of Texas was treated with liquid and dry formulations of herbicides. Sprays of Bay Met 1486 {N-[5-(ethylsulfonyl)-1,3,4-thiadiazol-2-yl]-N, N′-dimethylurea} and picloram (4-amino-3,5,6-trichloropicolinic acid), sprays and pellets of tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, and boluses of hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1N,3H)-dione] at 4.5 kg ae or ai/ha were the most effective treatments, reducing the canopy 87 to 99% and killing 68 to 93% of the yaupon after 2 yr. The percentage of dead yaupon after 1 yr was similar to that found 2 or 3 yr after treatment. Most herbicides, except clopyralid (3,6-dichloro-2-pyridinecarboxylic acid), reduced the yaupon canopy sufficiently to allow an increase in understory grass and broadleaf vegetation, particularly 1 yr after treatment.

Treatment of soil with fumigants to kill dormant weed seeds is a valuable practice but control in the surface one or two inches is often poor. This is because the fumigant vapors diffuse rapidly out of the soil into the atmosphere before building up a lethal concentration near the surface. Improved weed control has been reported by proper confinement of fumigant vapors in the soil with impervious seals. Water seals have been advocated by some workers as a satisfactory substitute for impervious covers. However, only limited experimental data are available comparing soil fumigation results with different methods of sealing the soil surface.

Control of littleseed canarygrass (Phalaris minor Retz.), wild oat (Avena fatua L.), common lambsquarters (Chenopodium album L.), and field bindweed (Convolvulus arvensis L.) in dwarf wheat (Triticum aestivum L.) fields was studied with five herbicides and hand weeding. Terbutryn [2-(tert-butylamino)-4-(ethylamino)-6-(methylthio)-s-triazine] and 1-benzthiazol-2-yl-1,3-dimethylurea controlled the weeds more effectively than did two hand weedings. Diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], nitrofen (2,4-dichlorophenyl p-nitrophenyl ether), and dichlormate (3,4-dichlorobenzyl methylcarbamate), proved only partially effective against weeds, and were therefore significantly inferior to two hand weedings. Spikes per meter of row length and test weight of wheat were increased significantly by 1-benzthiazol-2-yl-1,3-dimethylurea (1.5 to 2 kg/ha), terbutryn (0.5 kg/ha), and two hand weedings over the yields of the weedy check. The 1-benzthiazol-2-yl-1,3-dimethylurea showed a high degree of selectivity in the wheat crop at 2 kg/ha and increased yields to those of weed-free plots. Terbutryn was almost as effective as 1-benzthiazol-2-yl-1,3-dimethylurea, which increased the wheat yields over those of the weedy check by 19.8 and 42.4% during the 1974/75 and 1975/76 seasons, respectively. Tolerance of dwarf wheat to terbutryn at 0.75 kg/ha was variable, resulting in significant decreases in yield components and grain yield. Dry-matter yield of wheat was negatively correlated with the dry matter production of weeds.

Applying control measures when carbohydrate levels are low can decrease the likelihood of plant survival, but little is known about the carbohydrate cycles of dewberry (Rubus spp.), a problematic weed group on cranberry (Vaccinium macrocarpon Aiton) farms. Weedy Rubus plants were collected from areas adjacent to production beds on commercial cranberry farms in Massachusetts, two locations per year for 2 yr. For each site and year, four entire plants were collected at five phenological stages: budbreak, full leaf expansion, flowering, fruit maturity, and after onset of dormancy. Root sections were analyzed for total nonstructural carbohydrates (TNC; starch, sucrose, fructose, and glucose). Overall trends for all sites and years showed TNC were lowest at full leaf expansion or flowering; when sampled at dormancy, TNC concentrations were greater than or equal to those measured at budbreak. Starch, a carbohydrate form associated with long-term storage, had low levels at budbreak, leaf expansion, and/or flowering with a significant increase at fruit maturity and the onset of dormancy, ending at levels higher than those found at budbreak. The concentration of soluble sugars, carbohydrate forms readily usable by plants, was highest at budbreak compared with the other four phenological samplings. Overall, our findings supported the hypothesis that TNC levels within the roots of weedy Rubus plants can be predicted based on different phenological growth stages in Massachusetts. However, recommendations for timing management practices cannot be based on TNC cycles alone; other factors such as temporal proximity to dormancy may also impact Rubus plants recovery, and further research is warranted. Late-season damage should allow less time for plants to replenish carbohydrate reserves (before the onset of dormancy), thereby likely enhancing the effectiveness of weed management tactics over time. Future studies should consider tracking the relationship between environmental conditions, phenological stages, and carbohydrate trends.