bluuebunny/crossref_metadata_2025 huggingface dataset:
Incident photosynthetically active radiation as a basis for integrated management of purple nutsedge (Cyperus rotundus)
Authors: Neeser Christophe , Aguero Renan , Swanton Clarence J.
Published: May 2019

Artificial shading studies indicated that competition for photosynthetically active radiation (PAR) will limit tuber production in purple nutsedge. There were no data available to test whether there is a relationship between incident PAR underneath crop canopies and tuber production of this weed. In this study, the effect of crop competition on net reproductive rates of purple nutsedge tubers was measured under field conditions. Purple nutsedge plants were grown in association with bush beans, maize, maize and beans intercropped, sweet potato, pole beans, and bell pepper in a 2-yr field study in Costa Rica. Measurements were taken on the number of tubers produced during the growing season of each crop, and PAR transmittance was monitored weekly for the duration of the respective cropping cycles. Data on transmittance and incident solar radiation were used to calculate the daily average amount of PAR, available 15 cm above the soil surface. Regressions indicated that average incident PAR accounted for 95% of the variation in net reproductive rates. Average incident PAR also allowed a more precise competitive ranking of crops than either average or minimum transmittance. Bush beans had consistently the lowest average incident PAR values and therefore ranked as the most competitive crop in both years. Our data suggest that no net increase in tuber populations occurs if average incident PAR is below 2.7 MJ m−2d−1. Differences in the duration of the cropping cycle accounted only for a small proportion of the overall variation in net reproductive rates of purple nutsedge tubers. Information on the competitive ranking of different crops can be used to design crop rotations that could reduce reliance on herbicides on small farms in Costa Rica.
Survival and dormancy of purple nutsedge (Cyperus rotundus) tubers
Authors: Neeser Christophe , Aguero Renan , Swanton Clarence J.
Published: May 2019

Survival and dormancy of purple nutsedge tubers has not been studied quantitatively. Yet this is fundamental to our understanding of the population dynamics of this highly noxious weed. Field studies were conducted to determine the effect of age on tuber survival and dormancy. A modified exponential decay function accurately described the age-dependent decline in tuber survival. This model is biologically meaningful, has good statistical properties, and can describe a wide range of responses. Tuber population half-life was 16 mo, and the predicted longevity (99% mortality) was 42 mo. Burial depth at 8 and 23 cm had no significant effect on survival or dormancy. Tuber dormancy increased with age. After 18 mo, the proportion of dormant tubers in the surviving population was two-and-one-half times higher than in the 3-mo-old population. We report for the first time that tubers were able to enter a state of secondary dormancy after sprouting. The finding that tubers persist after sprouting has important implications for population dynamics of this species. This is also the first report of tuber predation by the larvae of a billbug.
Efficacy of reduced rates of quinclorac applied with propanil or propanil plus molinate in dry-seeded rice (Oryza sativa)
Authors: Jordan David L.
Published: May 2019

Research was conducted from 1994 through 1996 to evaluate barnyardgrass control, rice yield, and estimated economic return with postemergence applications of propanil or propanil plus molinate applied alone or with quinclorac. Herbicides were applied at rates of 3.4, 2.8 + 2.8, and 0.17 to 0.40 kg ai ha−1for propanil, propanil plus molinate, and quinclorac, respectively. In most trials, combinations of propanil or propanil plus molinate applied with quinclorac provided greater barnyardgrass control, rice yields, and estimated economic returns than herbicides applied alone. Propanil or propanil plus molinate applied with quinclorac at 0.28 kg ha−1was as effective as propanil or propanil plus molinate applied with quinclorac at 0.40 kg ha−1. Applying quinclorac at 0.17 kg ha−1with propanil plus molinate was as effective as applying quinclorac at 0.28 or 0.40 kg ha−1with these herbicides.
Soybean (Glycine max) influences metolachlor mobility in soil
Authors: Keller Kyle E. , Weber Jerome B.
Published: May 2019

This study was conducted to evaluate the mobility of14C-metolachlor over 1 yr for three seasons when applied preemergent to undisturbed field lysimeters with and without soybean representing cropped and noncropped zones, respectively. Leachate was collected weekly and analyzed for total14C, metolachlor, and metabolites. Lysimeters were removed, sectioned, and analyzed for14C. Sixty and 90 days after treatment (DAT), there was less soil water in lysimeters with soybean. Recovery of14C in lysimeters decreased with time and ranged from 54 to 74% 30 DAT followed by a slower rate of loss with 35 to 49% remaining 365 DAT. Comparable amounts of total14C were observed in soybean lysimeters as in fallow lysimeters 30, 60, and 90 DAT.14C distribution in the lysimeters, however, was quite different. Sixty and 90 DAT,14C mobility in soybean lysimeters was less than in fallow lysimeters. Also, less leachate was collected from soybean lysimeters, which resulted in later appearances and lesser amounts of14C in the leachate. Cumulative leachate from lysimeters with and without soybean 365 DAT contained 2% and 10 to 18% of the applied14C, respectively. Peak concentrations of14C in leachate from fallow columns occurred about 90 DAT and were two to 19 times higher than14C concentrations in leachate from soybean lysimeters. Metolachlor concentrations in leachate were well below the National Health Advisory level for drinking water in all cases. Apparent volatilization losses of14C amounted to 26 to 46% of the applied14C-metolachlor 30 DAT. These results suggest that herbicide mobility is different in cropped vs. fallow sites and possibly in intra- and interrow crop positions.
Effect of SAN 582 on sethoxydim efficacy in johnsongrass (Sorghum halepense) and soybean (Glycine max)
Authors: Scott Robert C. , Shaw David R. , Ratliff Randall L.
Published: May 2019

Laboratory studies were conducted to determine the effect of SAN 582 on the absorption, translocation, and metabolism of sethoxydim in johnsongrass and soybean.14C-sethoxydim absorption in johnsongrass and soybean was enhanced 4 h after application when tank mixed with SAN 582. Absorption in johnsongrass increased from 18% with14C-sethoxydim applied alone to 65% when applied with SAN 582. Absorption in soybean increased from 30% with14C-sethoxydim applied alone to 83% when applied with SAN 582. The addition of crop oil concentrate also enhanced foliar absorption of14C-sethoxydim. Eight hours after application, foliar absorption in johnsongrass increased from 22% with14C-sethoxydim applied alone to 61% when14C-sethoxydim was applied with crop oil concentrate. Foliar absorption in soybean increased from 38% with14C-sethoxydim applied alone to 59% when14C-sethoxydim was applied with crop oil concentrate. When14C-sethoxydim was applied in combination with crop oil concentrate and SAN 582, foliar absorption was 84% or more in both johnsongrass and soybean 4 h after application and did not increase over time. Minor differences in translocation were observed, but these differences were not sufficient to account for the increase in foliar activity observed when SAN 582 is tank mixed with sethoxydim. SAN 582 did not affect metabolism of sethoxydim in either species. Based on these data, it appears that SAN 582 increases the efficacy of sethoxydim by enhancing foliar absorption.
Weed flora and the relative importance of site, crop, crop rotation, and nitrogen
Authors: Andersson Torsten N. , Milberg Per
Published: May 2019

Weed species composition and density were recorded in three identical field experiments established 26 to 30 yr ago in southern Sweden. Each experiment compared three 6-yr crop rotations and four rates of nitrogen application. The rotations differed by having (1) a 2-yr rotational grassland, (2) a 2-yr mixed rotational grassland (legume/grass), or (3) spring wheat followed by fallow. Other crops in the rotations were winter turnip rape, winter wheat, spring oats, and spring barley. Using multivariate analyses, the relative importance of site, crop, crop rotation, and nitrogen application rate on the weed flora was determined. The greatest difference was found between sites, and the second most important factor was crop species. Nitrogen application rate weakly influenced the weed flora, while differences between crop rotations were hardly detectable.
Phytochrome-mediatedAmaranthusgermination II: development of very low fluence sensitivity
Authors: Gallagher Robert S. , Cardina John
Published: May 2019

This research was conducted to determine the environmental conditions necessary for development and expression of very low fluence (VLFR) germination sensitivity, and to determine the roles of type I phytochrome, gibberellic acid (GA) biosynthesis, and nitrate in this process. Redroot pigweed seed was subjected to pregermination incubation regimes of 5, 12, and 23 C for up to 21 d in a −1.2 MPa polyethylene glycol solution in the dark. Development of VLFR sensitivity was most pronounced at 23 C, and induction of germination by the lowest fluence tested (3 μmol m–2) was greater at a germination temperature of 30 than 20 C. In dormant smooth pigweed seed, development of VLFR sensitivity occurred only when seed was subjected to a prechilling treatment to overcome primary dormancy. The instability of the fluence response of seed subjected to pregermination conditions favorable for development of VLFR was consistent with type I phytochrome accumulation and degradation after photoconversion. In redroot pigweed seed, inhibition of GA biosynthesis during pregermination incubation resulted in the partial attenuation of VLFR sensitivity. The addition of 75 ppm nitrate to pregermination and germination media enhanced VLFR sensitivity. Our results suggest that development of VLFR sensitivity is due to cooperative action between type I phytochrome and phytochrome-independent GA biosynthesis. In the soil seedbank, this sensitivity may be augmented in elevated soil nitrate environments.
Morphological variation among hemp dogbane (Apocynum cannabinum) populations
Authors: Ransom Corey V. , Kells James J. , Wax Loyd M. , Orfanedes Michael S.
Published: May 2019

Experiments were conducted to examine morphological variation among hemp dogbane populations. Rootstocks collected from 16 sites throughout Michigan and Illinois were used to establish nurseries in East Lansing, MI, and Champaign, IL. Growth, stem characteristics, and leaf characteristics were measured for each ecotype at both nurseries. Differences among ecotypes were observed for all measurements except emergence date and growing degree days to emergence. The number of shoots per plot produced by the ecotypes ranged from 5 to 54 and shoot height ranged from 69 to 126 cm. Ecotypes spread laterally at different rates, with the most aggressive covering 19 times more ground area than the least aggressive. Total shoot dry weight accumulation varied greatly among ecotypes. Some ecotypes could be identified from others by their unique leaf shape. Shoot number, shoot height, and ground area covered were greater for plants grown in Michigan than in Illinois. Differences in growth and morphological characteristics among ecotypes were not correlated with the geographical region where they were collected. Differences in measurements between the two nurseries illustrate the role of environment and genetics in the growth and morphology of this plant species.
Comparative growth and development of four spurred anoda (Anoda cristata) accessions
Authors: VanGessel Mark J. , Schroeder Jill , Westra Philip
Published: May 2019

Field studies were conducted in Colorado and New Mexico to examine growth and development of spurred anoda accessions from Colorado, Mississippi, New Mexico, and North Carolina. Accessions were grown in a common garden in both locations. Leaf and stem weight ratios, leaf area ratio, and leaf area per plant were determined. North Carolina and Mississippi accessions were similar in morphology and appearance. Leaf shape, degree of pubescence, and coloration were different in the Colorado and New Mexico accessions. At both sites, the Colorado accession was taller and the canopy wider than other accessions. In Colorado in 1993, North Carolina and New Mexico accessions had the highest total weight followed by Colorado, then Mississippi. In 1994, final total weights of North Carolina, Mississippi, and New Mexico accessions were similar and greater than the Colorado accession. All accessions had similar final total weights in New Mexico in 1993. In 1994, Mississippi, North Carolina, and New Mexico accessions had similar total weights. The Colorado accession flowered earlier than other accessions. Seeds from Mississippi and North Carolina accessions grown in Colorado were heavier than the New Mexico or Colorado accession. This research demonstrates why making inferences of weed biology for variable species that occur over diverse geographic and climatic conditions is difficult and why regionally specific data are needed for variable species.
Merits of a weed-sensing sprayer to control weeds in conservation fallow and cropping systems
Authors: Blackshaw Robert E. , Molnar Louis J. , Lindwall C. Wayne
Published: May 2019

Field studies were conducted from 1993 through 1995 to determine potential reductions in herbicide use and associated cost savings by utilizing a weed-sensing sprayer, named Detectspray, to control weeds throughout the fallow season and to control perennial weeds after crop harvest. The Detectspray system gave comparable weed control to conventional broadcast spraying on 80% of the application dates and reduced glyphosate/dicamba use over the fallow season by 19 to 60%. This reduced herbicide use resulted in cost savings of $6 to $32 ha−1. A fallow treatment that combined two herbicide applications with the Detectsprayer plus one to two wide-blade tillage operations was less costly than conventional tillage at two of 11 sites and at all sites retained more surface crop residues to reduce the risk of erosion. Postharvest glyphosate use on quackgrass with the Detectsprayer was reduced 50 to 78% compared to broadcast applications and resulted in cost savings of $16 to $25 ha−1. Clopyralid use on Canada thistle with the Detectsprayer was reduced 71 to 80%, with cost savings of $44 to $50 ha−1. The Detectspray system is a useful tool to effectively manage weeds in conservation fallow and reduced tillage cropping systems.
Factors affecting the operation of the weed-sensing Detectspray system
Authors: Blackshaw Robert E. , Molnar Louis J. , Chevalier Duane F. , Lindwall C. Wayne
Published: May 2019

Field experiments were conducted for 3 yr to determine the effect of various biological and physical factors on the operation of the weed-sensing Detectspray system. Plant detection is achieved by sensors measuring differential reflectance of red and near-infrared wavelengths of light from green plants, crop residues, and soil. Weed detection was greatly reduced 70 to 80 min after sunrise and before sunset when operated at lat 50°N because of reduced solar irradiance. Tall, dense-standing crop stubble limited detection of small weeds at the soil surface. Weed detection varied with plant species. Canola with three to four leaves consistently was detected, but wheat or green foxtail usually required five to six leaves to be detected. Small weeds were detected if present at densities greater than 70 plants m−2. Growers and commercial applicators need to be aware of the limitations of the Detectspray system to use it effectively to control weeds with concurrent reductions in herbicide use.
Palmer amaranth (Amaranthus palmeri) and common waterhemp (Amaranthus rudis) resistance to selected ALS-inhibiting herbicides
Authors: Sprague Christy L. , Stoller Edward W. , Wax Loyd M. , Horak Michael J.
Published: May 2019

Imazethapyr-resistant biotypes of Palmer amaranth and common waterhemp were studied to determine the magnitude of resistance and cross-resistance to three acetolactate synthase (ALS)-inhibiting herbicides. Resistant biotypes of Palmer amaranth and common waterhemp demonstrated > 2,800- and > 130-fold resistance to phytotoxicity of imazethapyr compared to susceptible biotypes, respectively. Concentrations of imazethapyr required for 50% in vivo inhibition of ALS activity were at least > 13,100 and > 1,900 times greater for resistant biotypes of Palmer amaranth and common waterhemp, respectively, compared to susceptible plants. Resistant biotypes of both species demonstrated cross-resistance to the sulfonylurea herbicides thifensulfuron and chlorimuron at the whole plant and enzyme levels, indicating that a less sensitive ALS enzyme confers this resistance to these plants.
Survival of downy brome (Bromus tectorum) seed in four environments
Authors: Wicks Gail A.
Published: May 2019

Downy brome is one of the most troublesome winter annual weeds in winter wheat-fallow rotations in the central Great Plains. A 3-yr seed burial study was initiated to determine how long downy brome seed remained germinable when placed on the soil surface or 2.5 cm deep at four different times in four environments. Only 1 to 7% of the downy brome seed survived after 1 yr on the soil surface in chemical fallow and stubble mulch when deposited in August, but survival varied in September, October, and November. In 1970, a year with low fall and winter precipitation, 36 to 46% of the seed placed on the soil surface of chemical fallow in September, October, and November survived, compared with 1 to 8% for stubble mulch tillage. Early spring tillage covered more seed with soil, and downy brome seed survival decreased. When fall and winter precipitation was normal, stubble mulch and chemical fallow had 1 to 20% germinable seed remaining. Induced dormancy existed in some years. More downy brome seed survived when placed on the soil surface of crested wheatgrass sod (14 to 50%) than on smooth brome sod (0 to 36%). No differences existed among environments when downy brome seed was buried 2.5 cm deep. Only 0.4% of downy brome seed buried 2.5 cm survived after 1 yr when averaged across all environments.
Effect of volunteer barley (Hordeum vulgareL.) interference on field pea (Pisum sativumL.) yield and profitability
Authors: O'Donovan John T. , Blackshaw Robert E.
Published: May 2019

Relationships between volunteer barley plant density and both pea and volunteer barley yield were determined in field experiments conducted over 2 yr at Vegreville and Lethbridge, Alberta. Nonlinear regression analysis indicated that severe pea yield losses due to volunteer barley occurred at both locations. Averaged over both years, pea seed yield losses per volunteer barley plant (initial slopes) varied from 1.7% at Vegreville to 5.4% at Lethbridge. Based on certain assumptions, economic thresholds calculated from the equations were approximately 2 and 6 volunteer barley plants m−2at Lethbridge and Vegreville, respectively. Revenue from the volunteer barley seed partially alleviated the monetary losses caused by the reduced pea seed yield. The effects of pea density on pea and volunteer barley yield were inconsistent and marginal. This suggested that there was little advantage, in terms of increasing pea yield or reducing volunteer barley interference, to seeding pea above the recommended rate of 100 plants m−2.
Mechanisms of competition for light between rice (Oryza sativa) and redstem (Ammannia spp.)
Authors: Caton Barney P. , Foin Theodore C. , Hill James E.
Published: May 2019

Redstem is an important weed in California water-seeded rice fields because of its aquatic habit, wide distribution, interference with harvest, and resistance to the herbicide bensulfuron. Our objective was to understand the mechanisms of competition for light between rice and redstem, with the goal of improving redstem control. A replicated greenhouse experiment was done in 1993 and 1994. Rice was water-seeded at a rate of 400 seeds m−2, and redstem was seeded simultaneously at approximate densities of 0, 50, and 100 seeds m−2 in continuously flooded 0.77 m2 basins. Plants were harvested once at final harvest in 1993 and twice in 1994, with an additional nondestructive sampling 34 days after seeding (DAS). Despite slower early growth, redstem height exceeded rice height about 45 DAS. At the midseason harvest in 1994 (56 DAS), no effects of redstem competition on any rice response variables were detected. However, at final harvest (110 and 118 DAS, 1993 and 1994, respectively) redstem competition at both treatment densities reduced rice tiller density, panicle density, shoot drymass, and grain drymass. Redstem competition reduced rice growth only after penetrating the canopy. Shade cast by redstem through rice maturity decreased shoot and grain production and increased tiller mortality. Lodging caused by redstem further affected rice growth. Season-long competition from redstem at mean densities of 67 and 110 plants m−2 reduced rough rice yields 31 and 39%, respectively, making redstem the most competitive broadleaved rice weed yet studied. Improved understanding of rice-redstem interactions indicates that using alternative herbicides to bensulfuron is unlikely to increase yield losses to redstem, and that control may be improved by increasing rice plant densities or slightly delaying early season chemical control. Because these strategies are mechanistic, they may also be useful for controlling other rice weeds with growth patterns similar to redstem.
Economic evaluation of field bindweed (Convolvulus arvensis) control
Authors: Wiese Allen F. , Bean Brent W. , Salisbury Clay D. , Schoenhals Monty G. , Amosson Steve
Published: May 2019

This research compared seven field bindweed control treatments to a check in a 3-yr winter wheat-sorghum-fallow rotation. Treatments included 3 wk intervals of sweep tillage combined with one or two annual applications of 2,4-D (tillage and 2,4-D). Two other treatments were the same as tillage and 2,4-D, except dicamba or a mixture of picloram and 2,4-D were applied once in October after wheat harvest. A fourth treatment was identical to tillage and 2,4-D, except imazapyr was sprayed immediately after harvest of wheat. Also, three no-tillage systems using glyphosate and 2,4-D at monthly intervals were supplemented with either dicamba, picloram and 2,4-D, or imazapyr the same as in treatments involving tillage and 2,4-D. The check was sweep tilled every 6 wk. All treatments controlled field bindweed in one rotation of two fallow periods and two crops. After control was accomplished, wheat and sorghum yields were about twice the check. Using 1995 costs and returns, profit for an owner-operator for the two fallow periods and two crops was $123 ha−1for tillage and 2,4-D, compared to $19 ha−1for the check. Tillage and 2,4-D supplemented with picloram or imazapyr were almost as profitable as tillage and 2,4-D. Because of high herbicide cost and low yields, no-tillage treatments lost money. Profits with a 33:67 owner-tenant rental agreement were $105 and $21 ha−1, respectively, for owner and tenant using tillage and 2,4-D. With no field bindweed control practice, the tenant lost $33 ha−1and the owner made $51 ha−1.
The influence of seeding rate on weed control in small-red lentil (Lens culinaris)
Authors: Ball Daniel A. , Ogg Alex G. , Chevalier Peggy M.
Published: May 2019

Experiments were conducted at two sites for 2 yr in the Pacific Northwest dryland cropping region to determine if seeding rate of small-red lentil could enhance weed control with herbicides and increase lentil seed yield. At Pendleton, OR, and LaCrosse, WA, lentil was planted at 22 or 44 kg ha−1in one direction in all plots. In one-half of the plots, lentil was cross-seeded at right angles with an additional 22 kg ha−1to provide seeding rates of 22, 44, 22 + 22, and 44 + 22 kg ha−1. Seeding rate main plots were split into three herbicide treatments and an untreated control. Total weed density was reduced by increasing seeding rate at Pendleton both years when averaged over all herbicide treatments. Seeding rate reduced total weed density to a greater extent when herbicides did not adequately control weeds or when herbicides were not applied at Pendleton in 1992. Increased seeding rate also reduced total weed dry weight at Pendleton in 1992 and 1993 and at LaCrosse in 1993. The suppressive effect of increased seeding rate on weed dry weight was more evident when herbicides were not used or when herbicides gave only partial control. Herbicides generally reduced weed density, but the effectiveness of individual treatments was related to the weed species present and environmental conditions present in each experiment. Lentil aboveground dry weight production increased with seeding rate at both locations; however, only in 1 yr did lentil seed yield increase with seeding rate. The primary benefit from increased seeding rate in this study was to reduce weed density and dry weight.
Norflurazon adsorption and dissipation in three southern soils
Authors: Willian William T. , Mueller Thomas C. , Hayes Robert M. , Bridges David C. , Snipes Charles E.
Published: May 2019

Norflurazon adsorption and dissipation under field and laboratory conditions, and distribution within the soil profile were determined in three soils representative of cotton-growing regions of the southeastern U.S. Norflurazon adsorption was greater in soil from 0 to 8 cm in a Lexington silt loam (Tennessee) and a Beulah silt loam (Mississippi) than in a Dothan loamy sand (Georgia). Adsorption was directly related to organic matter. Norflurazon degradation under controlled conditions in soil from 0 to 8 cm from each state was not different among locations, with half-lives ranging from 63 to 167 d. Degradation at 30 C in soil from the 30- to 45- and 60- to 90-cm depths was not different among locations, and was slower at the 60- to 90-cm depth than in surface soil. Norflurazon dissipation was more rapid under field conditions than under laboratory conditions, with half-lives ranging from 7 to 79 d in the 0- to 8-cm soil horizon. Dry field conditions slowed norflurazon dissipation. Norflurazon was not detected below 15 cm in the profile in any soil, and concentrations in the 8- to 15-cm soil zone were < 36 ppbw 112 d after treatment.
Implications of weed seedbank dynamics to weed management
Authors: Buhler Douglas D. , Hartzler Robert G. , Forcella Frank
Published: May 2019

The species composition and density of weed seed in the soil vary greatly and are closely linked to the cropping history of the land. Altering tillage practices changes weed seed depth in the soil, which plays a role in weed species shifts and affects efficacy of control practices. Crop rotation and weed control practices also affect the weed seedbank. Information on the influence of cropping practices on the weed seedbank should be a useful tool for integrated weed management. Decision aid models use information on the weed seedbank to estimate weed populations, crop yield loss, and recommend weed control tactics. Understanding the light requirements of weed seed may provide new approaches to weed management. Improving and applying our understanding of weed seedbank dynamics is essential to developing improved weed management systems. The principles of plant ecology must be integrated with the science of weed management to develop strategies that take advantage of basic plant responses in weed management systems for agronomic crops.
Absorption and translocation of glufosinate on four weed species
Authors: Steckel Gregory J. , Hart Stephen E. , Wax Loyd M.
Published: May 2019

Greenhouse and laboratory experiments were conducted to evaluate foliar absorption, translocation, and efficacy of glufosinate on four weed species. The rate of glufosinate required to reduce shoot dry weight by 50% (GR50) varied between weed species. GR50values for giant foxtail, barnyardgrass, velvetleaf, and common lambsquarters were 69, 186, 199, and 235 g ai ha−1, respectively. Absorption of14C-glufosinate increased with time and reached a plateau 24 hours after treatment (HAT). Absorption of14C-glufosinate was 67, 53, 42, and 16% for giant foxtail, barnyardgrass, velvetleaf, and common lambsquarters, respectively. Translocation of absorbed14C-glufosinate from the treated leaf was greatest for giant foxtail and barnyardgrass (15 and 14% 24 HAT of absorbed14C-glufosinate, respectively). This compared to 5 and < 1% for translocation of absorbed14C-glufosinate from the treated leaves of velvetleaf and common lambsquarters. The majority of14C-glufosinate translocated by giant foxtail and barnyardgrass was found below the treated leaf and in the roots, indicating phloem mobility of the herbicide. Differential absorption and translocation of14C-glufosinate may be contributing factors to the differential sensitivity observed between weed species.
Germination, emergence, and growth of giant foxtail (Setaria faberi) and fall panicum (Panicum dichotomiflorum)
Authors: Fausey Jason C. , Renner Karen A.
Published: May 2019

Controlled environment experiments were completed to determine the effect of temperature on giant foxtail and fall panicum germination, emergence, and growth. Giant foxtail seed germination decreased when exposed to a constant 30 C compared to 20 C. Germination also decreased in the alternating 20/30 C temperature regime when the hours of exposure to 30 C as compared to 20 C increased. Fall panicum required alternating temperatures of 14 C (9 h)/28 C (15 h) to germinate. Giant foxtail seed germination exceeded 60% 4 d after exposure to an alternating temperature of 7 C (9.4 h)/20 C (14.6 h). Conversely, fall panicum seed did not germinate at the 7 C (9.4 h)/20 C (14.6 h) temperature regime and required a minimum of 7 d exposure to alternating temperatures of 13 C (8.7 h)/26 C (15.3 h) for 88% of the seed to germinate. The greatest emergence of giant foxtail and fall panicum was from 1 cm and 1 to 2.5 cm, respectively. Less than 5% of the giant foxtail and fall panicum seed emerged from 7.5 cm. The growth of giant foxtail seedlings was five times greater than that of fall panicum at each temperature regime tested. Incorporation of this information into bioeconomic models could result in accurate predictions of weed germination for effective weed management strategies.
Fluctuating temperature and light influence seed germination of goosegrass (Eleusine indica)
Authors: Nishimoto Roy K. , McCarty Lambert B.
Published: May 2019

This research examined the effect of duration of the warm cycle and number of fluctuating temperature/light cycles on goosegrass seed germination. Less than 10% goosegrass seed germination occurred at constant temperatures of 20, 25, and 35 C, while 99% germinated at daily fluctuating temperature regimes of 20 C for 16 h and 35 C for 8 h with light. Increasing the number of fluctuating temperature cycles increased goosegrass seed germination. Fluctuating temperature cycles with 22 h at 20 C and 2 h at 35 C with light strongly stimulated germination, but not as much as the cycle with 8 h at 35 C. Goosegrass seed germination ceased once the fluctuating temperature regime was discontinued, and constant 20 C with 8 h light daily was reimposed. Germination occurred only on resumption of fluctuating temperature cycles. Seed incubated for several weeks in a moist environment at constant 20 C had 81 to 91% germination with two cycles of 20 C for 16 h and 35 C for 8 h, compared to 14% for fresh seeds.
Interacting effects of MON 12000 and CGA-152005 with other herbicides in velvetleaf (Abutilon theophrasti)
Authors: Hart Stephen E.
Published: May 2019

Greenhouse and laboratory studies were conducted to determine the effects of dicamba, atrazine, and bentazon on efficacy, foliar absorption, and translocation of MON 12000 or CGA-152005 applied to velvetleaf. The efficacy of MON 12000, CGA-152005, and a combination of CGA-152005 plus primisulfuron applied at 4.5 g ai ha−1was similar when applied alone or with 140 g ha−1of dicamba. However, applying these herbicides in combination with 840 or 560 g ha−1of atrazine or bentazon, respectively, reduced velvetleaf control. Increasing the rate of MON 12000, CGA-152005, or the combination of CGA-152005 plus primisulfuron to 9 g ai ha−1or replacing crop oil concentrate (COC) with methylated seed oil (MSO) increased velvetleaf control of the atrazine and bentazon combinations but not to levels equal to these herbicides applied alone. Dicamba had no effect on the foliar absorption and translocation of14C from MON 12000 or CGA-152005. Atrazine had little effect on foliar absorption of14C from MON 12000 or CGA-152005, but bentazon reduced the foliar absorption of14C from MON 12000. Replacing COC with MSO increased the foliar absorption of14C from MON 12000 or CGA-152005 applied alone or with dicamba or atrazine, but not with bentazon. Translocation of14C from MON 12000 or CGA-152005 out of the treated leaves was 11 and 12%, respectively, averaged across adjuvants and sampling times. These values were reduced to an average of 3 to 4% for both MON 12000 and CGA-152005 when applied in combination with atrazine or bentazon. The majority of14C from MON 12000 or CGA-152005 was translocated acropetally. Atrazine and bentazon significantly reduced the acropetal translocation of14C from MON 12000 at 24 and 72 h and for CGA-152005 at 12, 24, and 72 h. The physiological basis for the observed antagonism of MON 12000 and CGA-152005 by atrazine and bentazon appears to be due to reductions in acropetal translocation of MON 12000 and CGA-152005 to velvetleaf meristems.
Weed suppression withBrassicagreen manure crops in green pea
Authors: Al-Khatib Kassim , Libbey Carl , Boydston Rick
Published: May 2019

Weed suppression in green pea was evaluated when green pea was planted after a fall planting of rapeseed, white mustard, rye, or wheat had been incorporated into the soil in spring. Tests were conducted at Mount Vernon, WA, in 1994 and 1995. Weed suppression in peas varied between different green manure crops. One month after planting, the highest weed population was in green pea following wheat, whereas the lowest was in green pea following rapeseed. Rye and white mustard suppressed early weeds relative to wheat by 25 and 30%, respectively. However, at harvest, weed density was similar in green pea planted after all green manure crops. Weed suppression improved when cultivation or metribuzin at 0.14 kg ha−1was used in combination with white mustard, rapeseed, or rye. Pea population was not affected by green manure crops, except for rapeseed, which reduced pea population. In greenhouse experiments, white mustard added to the soil at 20 g per 400 g air dry soil reduced emergence of shepherd's-purse, kochia, and green foxtail by 97, 54, and 49%, respectively. Rapeseed suppressed emergence of shepherd's-purse, kochia, and green foxtail by 76, 25, and 25%, respectively.
Genetic variation in North American leafy spurge (Euphorbia esula) determined by DNA markers
Authors: Rowe Martha L. , Lee Donald J. , Nissen Scott J. , Bowditch Brunella M. , Masters Robert A.
Published: May 2019

Levels of inter- and intrapopulation genetic variation were determined in five North American populations of leafy spurge using chloroplast DNA (cpDNA) RFLPs and RAPD markers. Thirteen plastome types were identified among 123 individuals collected from five geographically separated populations. Number of plastomes within a population ranged from one to seven, with four of the populations having a predominate type plus one or more rarer types. Some plastome types were shared by populations, but plastome distribution among populations was nonrandom. RAPD markers indicated greatest relatedness among individuals within a population. Relatedness among populations as established through RAPDs was greater for geographically closer populations; this relationship was not observed for cpDNA markers. Differences in the range of movement for pollen and seed may account for differences between results of the cpDNA and RAPD analyses. The high degree of genetic variability among North American leafy spurge suggests possible multiple introductions or a high degree of variability within leafy spurge populations in its native range.
Geographic variation and conservation of the Moustached Woodcreeper Xiphocolaptes falcirostris, an endemic and threatened species of north-eastern Brazil
Authors: da Silva José Maria Cardoso , Oren David C.
Published: May 2019

We correct the limits of the range and analyse the geographical variation of the Moustached Woodcreeper Xiphocolaptes falcirostris, an endemic species of north-eastern Brazil. A single, undated specimen of Moustached Woodcreeper from Posse, Goiás, in the Paranā River Valley was probably collected somewhere on the left bank of the Sāo Francisco River. Analysis of the plumage variation and five body measurements indicates that it is not always possible to separate the populations of the Moustached Woodcreeper into the two subspecies currently recognized. In spite of this, given the importance of this bird as an indicator species for conservation, we suggest that the current recognition of the subspecies be maintained until genetic studies provide a definitive answer to this taxonomic question. Moustached Woodcreepers are particularly associated with patches of dry forest growing on rich soils, in north-eastern Brazil. In the past decades, this type of vegetation has been drastically modified by human activities. Only an urgent plan to establish a network of reserves for tropical dry forests in north-eastern Brazil can prevent the complete destruction of this habitat and of its poorly known biological resources.

Nós corrigimos os limites da distribuiçāo e analisamos a variaçāo geográfica do Cochi-do-nordeste Xiphocolaptes falcirostris, uma espécie endêmica do Nordeste brasileiro. Um único espécime sem data de X. falcirostris coletado em Posse, Goiás, no vale do rio Paranā, foi provavelmente coletado em algum lugar na margem esquerda do vale do rio Sāo Francisco. Análise da variaçāo da plumagem e de cinco medidas do corpo indicam que nāo é sempre possivel separar as populaçōes de Cochi-do-nordeste em duas subespécies, tal como é feito atualmente. Apesar disso, em consideraçāo à importância desse arapacu como espécie indicadora, nós sugerimos que o Cochi-do-nordeste ainda seja considerado uma espécie com duas subéspecies, até que essa questāo taxonômica seja resolvida definitivamente através de estudos genéticos. Cochis-do-nordeste sâo particularmente associados com manchas de florestas secas crescendo sobre solos ricos no Nordeste brasileiro. Nas ultimas décadas, este tipo de vegetaçāo tem sido drasticamente modificado por atividades humanas. Nós sugerimos que somente um piano urgente visando o estabelecimento de um sistema de reservas para as florestas tropicais secas no nordeste do Brasil possa prevenir a completa destruiçāo desse habitat e de seus pouco conhecidos recursos biológicos.
A note on 20-species lists
Authors: Poulsen Bent Otto , Krabbe Niels , Frølander Amy , Hinojosa Marcelo B. , Quiroga Carmen O.
Published: May 2019

Since our paper on the efficiency and biases of 20-species lists (Poulsen et al. 1997) went to press we have recognized a further two biases in the method, after discussions with C. Rahbek. We remarked in our paper that the abundance curves were behaving rather strangely and that “the importance of these phenomena needs to be investigated in more detail”. The behaviour may be due to the method setting constraints on the highest possible frequency, namely the number of times a species occurs in 20-species lists. This could affect the calculation of the expected abundances and hence the a-index. Another bias must be the indirect way of determining the relative abundances, ignoring the true number of individuals. A species with many individuals will be given the same relative abundance as a species with very few individuals if both species occur in the same number of 20-species lists. We do not know the importance of these constraints but recommend that the method is not used until the results of a current computer modelling study examining its efficiency (S. Herzog and M. Kessler pers. comm.) are known.
Len Cosson Memorial Lecture. Special Education Policy for Children with Moderate Learning or Behavioural Difficulties in New Zealand: Does “Inclusion” Really Mean “Exclusion“?
Authors: Wilton Keri
Published: May 2019

This invited Lecture is held at each National Conference of the New Zealand Special Education Association to honour the memory of Len (Leyland Duvalle) Cosson (1933–1987), and is sponsored by the Len Cosson Memorial Trust. Len was a distinguished New Zealand special educator, and at the time of his untimely death he was Principal Lecturer in Special education at Christchurch College of Education. At Christchurch, had established New Zealand’s first special 1‐year training course for teachers in special education; he wrote many influential handbooks and articles aimed at improving teaching practice in special education; and played a major role in the establishment of NZSEA.
Quality of School-based Physical Education and Sport for Students with Disabilities in Western Australia
Authors: Lockwood Richard , Lockwood Anne
Published: May 2019

The relative quality of Physical Education and Sport for students with and without disabilities was examined by surveying the views of students, teachers, and support staff in a sample of West Australian schools. The findings indicate differences in quality of Physical Education and Sport for students with and without disabilities. Students with disabilities did not receive the same quality of Physical Education and Sport experiences, although they tended to be enthusiastic about what they did receive. A higher proportion of this group completed activities other than fully participating in Physical Education and Sport. Depending on individual circumstances, this may suggest that in addition to the inclusion model, there may be a need to establish parallel or segregated and personalised programs for some students. The findings also highlighted the urgent need for (a) inclusionary practice to be an integral part of pre‐service teacher education, (b) a range of professional development and networking opportunities for teachers of Physical Education, and (c) greater resources to be allocated for equipment, facilities and support staff to assist students with disabilities.
Inside Four Walls
Authors: Forlin Chris
Published: May 2019

This research study was designed to investigate the effects of inclusion on regular class teachers in Queensland schools. While education departments promote inclusion there is frequently insufficient notice taken of the impact of such programs within the classroom context where inclusion actually happens. For the majority of children, and for most of the time, inclusion occurs within the four walls of a regular classroom. This paper reports the findings of focus group interviews with primary school teachers involved with inclusion. The research was undertaken in 1997 with 17 teachers from 13 primary schools within one region in Queensland. All teachers involved in this study taught in regular classrooms that included a child with either an intellectual or physical disability. Discussion of the analysis of the interviews focuses on three main areas within the classroom context: (1) the children in the classes (2) the classroom learning environments; and (3) the teachers. This project is highly significant as policies of inclusion rely on teachers’ acceptance of them, belief in their worth, and ability to cope. It is essential to determine if the reality of the current situation is likely to support further trends towards greater inclusion.
A Study of the Impact of Preschool Integration on Children Without Disabilities in their First Year of School
Authors: Lepelaar Astrid , Kemp Coral
Published: May 2019

Eight children without disabilities who attended an inclusive preschool at Macquarie University Special Education Centre were followed‐up in their first year of school in an attempt to establish whether their preschool program, in particular the inclusion of a high proportion of children with a range of intellectual disabilities, would have a detrimental effect on their subsequent social and academic performance. The current skills of these children, in relation to their peers, were assessed using a range of measures including a teacher interview, a collection of independently evaluated work samples and measures of in‐class behaviour. The academic performance of the children was also compared to the measures of their receptive vocabulary and tests of early reading which were collected towards the end of their preschool year. The academic and social measures taken in the school year indicated that the children’s performance was equal to that of their peers, thereby challenging claims that integrated settings have a negative impact on development. According to the ratings of their early reading and phonemic awareness skills by their kindergarten teachers, these children were performing at or above the level predicted by measures of their language and prereading skills in the preschool.
Effective Teaching for Students with Asperger’s Syndrome in the Regular Classroom
Authors: le Roux Johann , Graham Lorraine , Carrington Suzanne
Published: May 2019

This paper investigates issues surrounding the inclusion of students with Asperger’s Syndrome in primary school classrooms by first identifying the unique needs of these students, and secondly, by examining some strategies which can facilitate the inclusion of these students into inclusive school settings. These effective methods take into account physical factors within the classroom, the predictability of instructional routines, and building on students’ pre‐existing knowledge in order to enhance their productivity. The approaches to instruction discussed in this paper are particularly valuable because they are appropriate to the needs of many students in the regular classroom.
Examination of Atomic (Scanning) Force Microscopy Probe Tips with the Transmission Electron Microscope
Authors: DeRose J.A. , Revel J.-P.
Published: May 2019

Abstract: We have developed a method for the examination of atomic force microscopy (scanning force microscopy) tips using a high-resolution transmission electron microscope (TEM). The tips can be imaged in a nondestructive way, enabling one to observe the shape of an atomic force microscope probe in the vicinity of the apex with high resolution. We have obtained images of atomic force microscopy probes with a resolution on the order of 1 nm. The tips can be imaged repeatedly, so one can examine tips before and after use. We have found that the tip can become blunted with use, the rate of wear depending upon the sample and tip materials and the scanning conditions. We have also found that the tips easily accrue contamination. We have studied both commercially produced tips, as well as tips grown by electron beam deposition. Direct imaging in the TEM should prove useful for image deconvolution methods because one does not have to make any assumptions concerning the general shape of the tip profile.
Structural Characterizations of Bi2Sr2CaCu2O8+δ Twist Boundaries Using Advanced Transmission Electron Microscopy
Authors: Zhu Yimei , Wu L. , Wang J.-Y. , Li Q. , Tsay Y.N. , Suenaga M.
Published: May 2019

Structural Characterizations of Bi2Sr2CaCu2O8FATAL ERROR -- Missing abstract.plus;FATAL ERROR -- Missing abstract.dgr; Twist Boundaries Using Advanced Transmission Electron Microscopy