Effects ofEriochloa villosadensity and time of emergence on growth and seed production inZea mays

Weed Science ◽  
1999 ◽  
Vol 47 (6) ◽  
pp. 687-692 ◽  
Author(s):  
James A. Mickelson ◽  
R. Gordon Harvey
Keyword(s):  
Seed Production ◽  
Field Experiments ◽  
Seed Mass ◽  
Model Parameters ◽  
Growth Stages ◽  
Vegetative Biomass ◽  
Eriochloa Villosa ◽  
Term Management ◽  
Weed Emergence

Field experiments were conducted in 1997 and in 1998 to determine the effects of density and time of emergence onEriochloa villosagrowth and seed production inZea mays. E. villosawas transplanted at four densities (3, 9, 27, and 81 plants m−2) to simulate emergence at four Z.maysgrowth stages (VE, V2, V5, and V10). Compared toE. villosaplants that emerged withZ. maysplants, total above-groundE. villosabiomass at maturity of plants grown at 3 plants m−2was reduced by 54, 97, and 99% when emergence was delayed until the V2, V5, and V10 stages ofZ. mays, respectively, in 1997. In 1998, total abovegroundE. villosabiomass at maturity was reduced by 70, 87, and 99% when emergence was delayed until the V2, V5, and V10 stages ofZ. mays, respectively.E. villosaaboveground vegetative biomass per plant at maturity was linearly related to seed production per plant in each year.E. villosaseed production m−2decreased nonlinearly as density decreased and time of emergence was delayed. Based on estimated model parameters, maximum seed production was 57,100 and 12,700 seeds m−2in 1997 and 1998, respectively. Within time of emergence,E. villosadensity did not affect seed mass per seed, however, seed mass of late-emerging cohorts was less than that of early-emerging cohorts. Time of weed emergence relative to the crop was a very important factor in determining biomass and seed production. Results suggest that late-emerging plants may not be very important to long-term management ofE. villosa.

Management of Avena ludoviciana and Phalaris paradoxa with barley and less herbicide in subtropical Australia

2001 ◽  
Vol 41 (8) ◽  
pp. 1179 ◽  
Author(s):  
S. R. Walker ◽  
G. R. Robinson ◽  
R. W. Medd
Keyword(s):  
Seed Production ◽  
Weed Management ◽  
Field Experiments ◽  
Management Strategies ◽  
Maximum Yield ◽  
Yield Reduction ◽  
Weed Seed ◽  
Tiller Density ◽  
Weed Emergence ◽  
Subtropical Australia

The competitive advantage of barley compared with wheat was quantified for suppressing seed production of Avena ludoviciana Durieu. (wild oats) andPhalaris paradoxa L. (paradoxa grass), and for improving herbicide effectiveness on these major winter grass weeds of the subtropical grain region of Australia. Eight field experiments were broadcast with weed seed before sowing wheat or barley, in which the emerged weeds were then treated with 4 herbicide doses (0, 25, 50, 100% of recommended rates). Yield reduction from untreated weeds was on average 4 times greater in wheat than in barley, with greater losses from A. ludoviciana than P. paradoxa. Barley did not affect weed emergence, but suppressed weed tiller density and, to a lesser extent, the number of weed seeds per tiller. Seed production was, on average, 4340 and 5105 seeds/m2 for A. ludoviciana and P. paradoxa, respectively, in untreated wheat compared with 555 and 50 seeds/m2 in untreated barley. Weed seed production following treatment with 25% herbicide rate in barley was similar or less than that after treatment with 100% herbicide rate in wheat. Overall, 25% herbicide rate was optimal for both conserving yield and minimising weed seed production in barley. For wheat, maximum yield was achieved with 50% herbicide but weed seed production was lowest with 100% herbicide rate. This indicates that weeds can be effectively controlled in barley with considerably less herbicide than required in wheat, highlighting the importance of including barley as a part of weed management strategies that aim to reduce herbicide inputs.

Seed biology of jubatagrass (Cortaderia jubata)

Weed Science ◽  
2004 ◽  
Vol 52 (4) ◽  
pp. 525-530 ◽  
Author(s):  
Jennifer J. Drewitz ◽  
Joseph M. DiTomaso
Keyword(s):  
Field Experiments ◽  
Control Program ◽  
Nonnative Species ◽  
Coastal Environments ◽  
Natural Conditions ◽  
Seed Biology ◽  
Primary Dormancy ◽  
Viable Seeds ◽  
Term Management

Jubatagrass is one of the most invasive nonnative species along sensitive natural coastal sites of California. This study was designed to understand the biology of reproduction and seed longevity under field conditions. Jubatagrass can produce over 100,000 wind-dispersed seeds from a single inflorescence. Seeds are produced apomictically, and germination is directly related to seed size. Of the total seeds produced, only 20 to 30% were of ample size to readily germinate when exposed to light and under a temperature range similar to coastal environments. Seeds not exposed to light also germinated but at about 30% the level of light-exposed seeds. This suggests that exposed disturbed coastal sites with moderate temperatures have high potential for germination and establishment of jubatagrass. The percentages of germinable and viable seeds were not significantly different, indicating that jubatagrass does not have a primary dormancy. This was supported by field experiments demonstrating that seeds do not persist under natural conditions for more than 6 mo. These results indicate that an intensive 1-yr control program targeting established seedlings and mature plants should sufficiently manage existing populations. However, effective long-term management of jubatagrass must focus on anticipating environments susceptible to invasion, reducing new seed recruitment, and preventing subsequent seed germination and seedling establishment.

scholarly journals Impact of Brown Spot Caused by Septoria glycines on Soybean in Ohio

Plant Disease ◽  
2010 ◽  
Vol 94 (7) ◽  
pp. 820-826 ◽  
Author(s):  
Christian D. Cruz ◽  
Dennis Mills ◽  
Pierce A. Paul ◽  
Anne E. Dorrance
Keyword(s):  
Growth Stage ◽  
Yield Loss ◽  
Management Program ◽  
Brown Spot ◽  
Growth Stages ◽  
Yield Losses ◽  
Cultivar Development ◽  
Term Management ◽  
Different Levels

Brown spot, caused by Septoria glycines, is the most common foliar disease of soybean in Ohio, but its economic impact has not been assessed on modern cultivars. Therefore, the objectives of this study were to (i) evaluate the effect of S. glycines on soybean yield and (ii) evaluate the efficacy of strobilurin- and triazole-based fungicides on the control of brown spot. Yield loss associated with S. glycines was determined using weekly applications of chlorothalonil. The efficacy of azoxystrobin, pyraclostrobin, tebuconazole, and flutriafol alone and in combinations were also assessed using applications at the R3 and R5 growth stages at two locations over 3 years. Significantly different levels of brown spot developed following applications of chlorothalonil, with mean yield differences between treated and nontreated plots ranging from 196 to 293 kg/ha. Pyraclostrobin and azoxystrobin applied at the R3 growth stage significantly reduced final levels of brown spot; however, significant increases in yield occurred in only three of the six location-years. Triazoles, flutriafol and tebuconazole, applied at R3 or R5 did not significantly decrease levels of brown spot or impact yield. More data on the accurate timing of fungicides are still required to establish a long-term management program for this disease, and resistance to brown spot should be monitored in soybean cultivar development to prevent future yield losses.

POST Herbicide Combinations for Velvetleaf (Abutilon theophrasti) Control in Sugarbeet

2011 ◽  
Vol 25 (1) ◽  
pp. 14-18 ◽  
Author(s):  
Miroslav Jursík ◽  
Josef Soukup ◽  
Veronika Venclová ◽  
Josef Holec
Keyword(s):  
Leaf Area ◽  
Seed Production ◽  
Laboratory Experiments ◽  
Field Experiments ◽  
Field Trials ◽  
Abutilon Theophrasti ◽  
Growth Stages ◽  
True Leaf ◽  
Cotyledon Stage ◽  
Pot Experiments

Velvetleaf is one of the most significant and fastest spreading alien weeds in Europe, and it is a difficult weed to control in conventional sugarbeet. Laboratory experiments were carried out in 2007 and 2008 and field experiments were carried out in 2006, 2007, and 2008 with the aim of finding effective herbicide combinations and optimum timing of control. Herbicides containing the active ingredients phenmedipham, desmedipham, ethofumesate, clopyralid, and triflusulfuron were all tested at different timings. Phenmedipham + desmedipham + ethofumesate gave 87% velvetleaf control in pot experiments when applied at the growth stages of velvetleaf cotyledons and one true leaf, but only 27 to 42% control in field trials. Triflusulfuron gave 76% control in pot experiments and 83 to 88% control in field experiments. The timing of the first and second herbicide applications was very important: the first application of herbicides must be at the cotyledon stage of velvetleaf. A 1-wk delay in first application reduced herbicide efficacy by 8%. A 5-d period between the first and second treatments gave 93% control, while a 10-d period between the first and second treatments gave only 77% control. Sugarbeet yield decreased by 60 to 86% due to competition with velvetleaf when a standard herbicide combination (phenmedipham + desmedipham + ethofumesate) was used, and the velvetleaf produced between 6,700 and 14,800 seeds m−2. Inclusion of triflusulfuron in the herbicide treatment significantly reduced velvetleaf seed production to between 200 and 4,700 seeds m−2. In most cases, inclusion of triflusulfuron increased sugarbeet yield. Better velvetleaf control occurred in years when the sugarbeet canopy developed early and the index of leaf area of sugarbeet was higher.

TOLERANCE OF CREEPING RED FESCUE AND TIMOTHY TO HERBICIDES USED TO CONTROL CANADA THISTLE

1976 ◽  
Vol 56 (2) ◽  
pp. 331-338 ◽  
Author(s):  
A. GALLAGHER ◽  
W. H. VANDEN BORN
Keyword(s):  
Seed Production ◽  
Field Experiments ◽  
Phleum Pratense ◽  
Treatment Result ◽  
Grass Species ◽  
Growth Stages ◽  
Canada Thistle ◽  
Red Fescue ◽  
Herbicide Treatments ◽  
Seed Crops

Field experiments at seven locations in northern Alberta confirmed that picloram (4-amino-3,5,6-tricholoropicolinic acid) is a useful herbicide for the control of Canada thistle (Cirsium arvense (L.) Scop.) in seed crops of creeping red fescue (Festuca rubra L.) and timothy (Phleum pratense L.). Dicamba (3,6-dicholoro-o-anisic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) were less effective. Preplant herbicide treatments were tolerated by both grass species provided that one growing season elapsed between treatment and planting of the grasses. Fertile tiller production was increased in plants selected from field plots treated 1 yr earlier with picloram and transferred to a growth chamber for flowering and seed production. Seed production of timothy was not affected by 0.14 – 0.84 kg/ha of picloram applied at several growth stages. Fescue seed production was not affected by picloram treatments up to 0.56 kg/ha, but was reduced by most other herbicide treatments applied at 10% anthesis. In no instance did herbicide treatment result in more than a 10% reduction in germination of seed from either grass species and, except in the case of a dicamba treatment on timothy, seedlings appeared to be normal in all respects.

Corn competition alters the germinability of velvetleaf (Abutilon theophrasti) seeds

Weed Science ◽  
2005 ◽  
Vol 53 (4) ◽  
pp. 479-488 ◽  
Author(s):  
Robert E. Nurse ◽  
Antonio DiTommaso
Keyword(s):  
Seed Production ◽  
Seed Coat ◽  
Cropping Systems ◽  
The United States ◽  
Planting Dates ◽  
Competitive Environments ◽  
Soil Seedbank ◽  
Growing Environment ◽  
Term Management

Velvetleaf is a troublesome annual weed in many cropping systems of the United States and Canada. Differences in the growing environment of parent plants can influence the number, structure, germinability, and viability of seeds produced. Thus, the effects across a range of competitive environments and corn planting dates on velvetleaf seed production, germination, and seed coat weight were examined under field conditions. Seed production of velvetleaf increased with increasing biomass. Total velvetleaf reproductive output was reduced in competition with corn compared with monoculture stands. Corn planting date had no effect on the dormancy status of seeds, but increased competition from corn resulted in up to a 30% decrease in the proportion of seeds that were dormant. Seed and seed coat weights also decreased for plants of velvetleaf grown in competition with corn compared with those grown in monoculture. These findings suggest that velvetleaf plants growing in relatively noncompetitive environments, such as along field edges or in field areas with poor crop stands, are likely not only to produce a greater number of seeds but also a greater proportion of seeds that are dormant. This alteration in the dormancy status of velvetleaf seeds in the absence or presence of a crop provides unique opportunities for effective long-term management of the soil seedbank in this species, especially for velvetleaf individuals bordering fields or growing in fallow areas that might require more stringent control because of increased seed dormancy.

scholarly journals Velvetleaf (Abutilon theophrasti Medik.) productivity in competitive conditions

2017 ◽  
Vol 69 (1) ◽  
pp. 157-166 ◽  
Author(s):  
Sava Vrbnicanin ◽  
Eleonora Onc-Jovanovic ◽  
Dragana Bozic ◽  
Marija Saric-Krsmanovic ◽  
Danijela Pavlovic ◽  
...  
Keyword(s):  
Seed Production ◽  
Weed Management ◽  
Intraspecific Competition ◽  
Field Experiments ◽  
Seed Mass ◽  
Abutilon Theophrasti ◽  
Plant Production ◽  
Major Influence ◽  
Area Index ◽  
Row Crops

Velvetleaf (Abutilon theophrasti Medik.) is an invasive alien species in many countries and one of the major weeds in summer row crops worldwide. Weed-management techniques that reduce weed production need to be investigated to provide new approaches. The first step in this process is the determination of weed productivity in different competitive conditions. Field experiments were conducted in 2006 and 2008 in an experimental field in Padinska Skela to quantify growth and seed production of velvetleaf in maize, as well as in a velvetleaf monoculture. A density of velvetleaf ranging from 1 to 8 plants m-1 was artificially created. In a mixture with maize, velvetleaf was sown in crop rows. The growth of velvetleaf was estimated based on plant height, fresh aboveground biomass and leaf area index (LAI). Velvetleaf fecundity was determined as seed mass plant-1 and seed mass m-2. Differences between years in plant production were very prominent. In general, velvetleaf productivity in maize depended on its density. Intraspecific competition had a major influence on growth and seed production when velvetleaf density was from 4 to 8 plants m-1 in maize rows. This information indicates that environmental conditions and weed density can promote/reduce inter- and intraspecific competition and help in the construction of population dynamics models to predict population density, seed bank and competitiveness of weeds and reduce inputs for weed management.

scholarly journals Seed production of two meadow fescue cultivars differing in growth habit

2008 ◽  
Vol 18 (1) ◽  
pp. 91 ◽  
Author(s):  
P. MÄKELÄ ◽  
M. KOUSA
Keyword(s):  
Seed Production ◽  
Seed Yield ◽  
Field Experiments ◽  
Seed Quality ◽  
Forage Quality ◽  
Biomass Accumulation ◽  
Meadow Fescue ◽  
Good Ability ◽  
Vegetative Biomass ◽  
Cultivation Technology

Meadow fescue (Festuca pratensis Huds.) is grown widely in the Nordic countries in forage grass mixtures. Locally adapted cultivars are preferred for establishment of mixed swards. Meadow fescue seed yield is determined by seed weight, the number of panicle bearing tillers, size of panicles and the number of fertile florets. We aimed to determine the differences in components of seed yield in two different meadow fescue cultivars differing in forage quality; Kalevi, released in 1979, and Fure, released in 1999. Biomass accumulation was monitored, numbers of fertile and sterile florets, and seeds were counted, and the forage quality was analysed. Seed quality was also analysed. Fure was leafier and accumulated more vegetative biomass than Kalevi. Kalevi had significantly more panicles than Fure, although Fure compensated for the lower number of panicles with increased panicle size. There were no differences in number of sterile and aborted florets between cultivars. Based on the results it seems that these two meadow fescue cultivars have a completely different strategy in seed production even though the final seed yield was not markedly different. It is apparent that meadow fescues have good ability to compensate among the components of seed yield. Long-term field experiments should be conducted to investigate the interactions between plant stand ecology, seed production and cultivation technology.;

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