Grafting is a common technique used to impart desirable traits to a plant’s scion. Herbicide resistant rootstocks have the potential to confer non–genetically modified (non-GM) scions with herbicide tolerance while mitigating some societal concerns regarding GM crops and food. We examined the impacts of soybean cultivar and growth stage and environmental temperature on transference of glyphosate tolerance to conventional (CN) soybean scions when grafted to glyphosate-resistant (RR) rootstocks. Small CN/RR (scion/rootstock) plants (3-leaf stage) and medium-sized plants (6-leaf stage) were injured more than large plants (10-leaf stage) 34 d after treatment (DAT) with 0.84 and 1.68 kg ae ha−1 glyphosate. All CN/CN combinations died, and RR/RR were uninjured. The cultivar of the scion had a greater effect on glyphosate tolerance than the cultivar of the rootstock. CN scions 352 and 5418 were more tolerant than CN scion 5388 across all RR rootstocks 35 DAT when treated with 0.84 kg ha−1 glyphosate. CN/RR construct 5388/9392 was more sensitive to temperature compared with 352/9392. Less leaf regrowth of 5388/9392 was observed under the warmer temperature. Our experiments demonstrated that grafting imparted robust glyphosate tolerance across different plant sizes, environmental temperatures, and scion/rootstock cultivars.

The effect of ethametsulfuron on populations of canola was evaluated in field and laboratory trials. Three canola populations (TR4, CB9604, and BC86-18) and the open-pollinated canola cv. ‘AC Parkland’ were treated with several doses of ethametsulfuron at the two- to four-leaf stage. In the field experiment, plant densities were determined before spraying and again at plant maturity. Density reductions during the growing season were observed for all populations (6 to 17%), but reductions due to ethametsulfuron above 0.3 g ha−1 depended on year, being noted for TR4 in 1997 (40 to 65%) only. In laboratory trials, only TR4 demonstrated sensitivity to ethametsulfuron, up to 49% visual damage averaged over all plants. The response was binary, with about 40% of plants at any given herbicide rate surviving unharmed and the remaining 60% of plants exhibiting > 90% visual damage. It is concluded that TR4 is sensitive to ethametsulfuron and further work, including a comprehensive genetic study, is required to determine the inheritance of sensitivity.

Three tractor cultivations that severely pruned the root systems of hand-weeded plots of sweet corn [Zea mays L. var. rugosa Bonaf., Iochief] grown on a Codorus-Elkton silt loam under extreme drought conditions did not reduce the yield of marketable ears when irrigation totalling 2 acre-inches was applied during pollination and ear-filling. Pre-emergence application of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine [atrazine] to the soil surface without cultivation reduced brace root growth and yields significantly in the year of most severe drought. These effects of atrazine were avoided when the herbicide treatments were supplemented with tractor cultivations that covered the brace root zone of the corn plants with soil.

Translocation of the 14C-labeled methazole [2-(3,4-dichlorophenyl)-4-methyl-1,2,4-oxadiazolidine-3,5-dione] was determined in cotton (Gossypium hirsutum L. ‘DPL 16′) from preemergence treatments and applications to leaves and stems in the field. Significantly greater methazole concentrations occurred in cotton from treatments to stems of 18 to 22-cm tall cotton than to leaves of 10 to 12-cm tall cotton or when applied preemergence. The radiolabel translocated primarily into the mature stems and leaves with lesser amounts translocating into the roots. Little 14C moved into the young growing points or into the seed and fiber of mature cotton. The distribution pattern of the 14C-label is characteristic of compounds which move primarily in the apoplast.

Fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] and tetrafluron {N,N-dimethyl-N′-[3-(1,1,2,2-tetrafluoroethoxy) phenyl] urea} are two urea-type herbicides for weed control in cotton (Gossypium hirsutum L.). In some years, because of cotton stand failure, an alternate crop must be established. Soybeans [Glycine max (L.) Merr.] and grain sorghum [Sorghum bicolor (L.) Moench] are possible alternate crops if they can withstand the residues left from herbicides used for weed control in cotton. Soybeans and grain sorghum were planted 3, 6 and 9 weeks after fluometuron and tetrafluron applications to soil at Knoxville and Milan, Tennessee, in 1975 and 1976. Tetrafluron residues were more toxic to grain sorghum and soybeans than were fluometuron residues. Grain sorghum was less susceptible than soybeans to both herbicides. Grain sorghum was planted 3 weeks after fluometuron (1.7 kg/ha) and tetrafluron (1.7 kg/ha) applications without severe yield reduction. Soybeans were planted in non-treated soil between banded tetrafluron (1.7 kg/ha on a treated area basis), 3 weeks after herbicide application, without significant yield reduction; but when a seedbed was prepared, a 9-week waiting period was required. When soybeans were planted into soil receiving a broadcast application of tetrafluron (1.7 kg/ha), a 9-week waiting period was not sufficient to reduce the residues to a non-toxic level. Soybeans planted 6 and 9 weeks following a broadcast application of fluometuron may or may not sustain yield reduction depending on rainfall frequency and intensity and soil type.

The historic maternal environment; the identity of competing, neighboring plants; and biotic stresses, such as fungal disease and herbivory, interact to influence the competitive ability, reproductive output, and plasticity of weed populations. A weed capable of altering its phenotype in response to environmental factors is better able to compete for resources in agroecosystems, thereby reducing crop yields and contributing more seeds to the seed bank. Velvetleaf is a highly competitive annual weed in many North American cropping systems, exhibiting a high degree of phenotypic plasticity in response to biotic and abiotic factors. We examined the effects of seed size (small and large), competitive environment (with and without soybean), and stress level (none = no treatment, moderate = pathogen inoculation, high = pathogen plus herbicide) on velvetleaf allometry and reproductive output during three field seasons. Only under the high-stress treatment was velvetleaf biomass, height, and reproductive output compromised (> 15% each), and these traits were further reduced with soybean competition. Soybean competition alone reduced velvetleaf biomass (> 50%), height (25%), and seed output (50%), but effects of competition varied with stress level. Velvetleaf plants that originated from large seeds (≥ 10 mg) generally outperformed plants originating from small seeds (< 10 mg) except under the high-stress treatment. These findings suggest that velvetleaf life-history traits and reproductive output in the current generation are a function of both present and historic factors. Management strategies for this species should involve tactics that not only reduce its competitive ability (e.g., biomass, height) but also decrease its seed production via synergistic stressors such as increased crop competitiveness, reduced-rate herbicide applications, and pathogen infection.

No differences in the anatomy or bud pattern development were observed between young tap and lateral roots of rush skeletonweed (Chondrilla juncea L.). Shoots and lateral roots arise from meristemic zones that originate from a continuous pericyclic ring. Incubation of excised root segments resulted in rapid development of stem buds which showed geotropic response in 24 h. The development of identifiable leaf initials occurred prior to emergence through the epidermis in 8 days.

Seeds of winged elm (Ulmus alata Michx.) stored under moist conditions lost viability rapidly. Under dry conditions the seeds lived longer. Winged elm seeds would not germinate at 4 C or 42 C but did at temperatures between these points. Salt concentrations above 20,000 ppm killed the seed; concentrations below this inhibited germination; twelve per cent manitol solutions (16 atmospheres osmotic pressure) prevented germination; pressures lower than this decreasingly affected germination. If the soil moisture level was below 2%, winged elm seeds would not germinate. Removal of the outer husk of the seed did not affect germination. Winged elm seedlings did not emerge if planted at depths below ¼ inch.

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.

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

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.

Promising results of applications of α, α-dichloropropionic acid (Dalapon) to wild oats (Avena fatua) were first reported in May 1953 in Dow Chemical Company's Dalapon Bulletin No. 1. Encouraging results with Dalapon on wild oats were obtained by various workers during the summer of 1953. The work reported herein was conducted in 1954 to gain further information on the effects of Dalapon on wild oats.

In a previous study Stadtherr and Widmer reported that several herbicides provided excellent weed control in field plantings of garden chrysanthemums (Chrysanthemum morifolium) The present study was undertaken (a) to compare the best herbicides of the previous study with newer materials, (b) to obtain additional data on herbicides which had been tested for one year only, and (c) to determine the effectiveness of herbicides applied in granular form.

Since the aerial brush control spraying operations in northern Minnesota have little research basis, the Lake States Forest Experiment Station has been carrying on some fundamental.studies aimed at improving the results of this increasingly important aid to forest management. These consist of analyzing two factors basic to all foliage spraying jobs whether they are done from the air or from the ground. These are:

1. The minimum amount of herbicide (in terms of acid equivalent) required to control a unit-area of brush of a given species and density, and

2. The minimum amount of solution needed to distribute the herbicide uniformly over the sprayed area.

Alligator juniper (Juniperus deppeana Steud.) is a weed tree of Arizona and New Mexico. It sprouts from stems, roots, or especially from buds on the crown, whenever the top is destroyed. Adequate mechanical control requires that the root crown be removed from the soil. Treatment of stumps with pelleted 3-phenyl-1,1-dimethylurea (fenuron) on the soil or polychlorobenzoic acid (PBA) sprayed on the stumps are promising means of preventing sprouting.

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.

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.

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.