Glyphosate-Resistant Palmer Amaranth (Amaranthus palmeri) Morphology, Growth, and Seed Production in Georgia

Weed Science ◽  
2015 ◽  
Vol 63 (1) ◽  
pp. 264-272 ◽  
Author(s):  
Theodore M. Webster ◽  
Timothy L. Grey
Keyword(s):  
United States ◽  
Seed Production ◽  
Growing Season ◽  
Palmer Amaranth ◽  
Competitive Balance ◽  
Potential Growth ◽  
Southeast United States ◽  
Alternative Means ◽  
Soil Seedbank ◽  
Crop Competition

Herbicide-resistant Palmer amaranth has become the most economically detrimental weed of cotton in the southeast United States. With the continual marginalization of potential herbicide tools, research has expanded to include alternative means of affecting future Palmer amaranth populations by altering safe sites and reducing inputs to the seedbank population. The influence of delayed Palmer amaranth establishment on seed production potential has not been investigated in the southeast United States. Studies were conducted to evaluate the influence of time of Palmer amaranth establishment on morphology, growth, and seed production. The experiment was a factorial, with five levels of Palmer amaranth transplanting (0 to 12 wk after cotton planting) and two levels of crop type (cotton and noncrop). In the absence of crop competition, the first cohort of Palmer amaranth produced 446,000 seeds per plant. This potential seed production was reduced 50% when Palmer amaranth plants were established nearly 6 wk later. In contrast, the first Palmer amaranth cohort growing in competition with cotton produced 312,000 seeds, 30% less than was produced in the absence of competition. Interference from cotton shifted time to 50% seed production to nearly 4 wk earlier in the growing season, relative to plants without crop competition. Delayed establishment of Palmer amaranth simulates premature loss of herbicide efficacy and alters the competitive balance between cotton and Palmer amaranth. Although the planting time that resulted in 50% reduction in Palmer amaranth plant height at the end of the season was not affected by the presence of cotton, 50% reduction in plant width and biomass occurred within the first 3.8 wk of the growing season when growing with cotton, more than 4 wk earlier than Palmer amaranth growing without a crop. This suggests that early season weed control programs will have a large effect on Palmer amaranth potential growth and seed production, as well as crop yield. To implement soil seedbank reduction strategies effectively, information on mechanisms that regulate Palmer amaranth persistence in the soil seedbank is needed.

scholarly journals Tall Waterhemp (Amaranthus tuberculatus) and Palmer amaranth (Amaranthus palmeri) Seed Production and Retention at Soybean Maturity

2016 ◽  
Vol 30 (1) ◽  
pp. 284-290 ◽  
Author(s):  
Lauren M. Schwartz ◽  
Jason K. Norsworthy ◽  
Bryan G. Young ◽  
Kevin W. Bradley ◽  
Greg R. Kruger ◽  
...  
Keyword(s):  
Seed Production ◽  
Plant Size ◽  
Palmer Amaranth ◽  
Weed Seed ◽  
Great Opportunity ◽  
Weed Biomass ◽  
Seed Retention ◽  
Loose Soil ◽  
Soil Seedbank ◽  
Total Seed

Two of the most problematicAmaranthusspecies in soybean production today are tall waterhemp and Palmer amaranth. This study determined the percentage of tall waterhemp and Palmer amaranth seed that was retained by the weed at soybean maturity to assess the likelihood of using at-harvest weed seed control tactics for soil seedbank management. Palmer amaranth plants were collected from fields in Arkansas, Tennessee, Illinois, Missouri, and Nebraska, and tall waterhemp plants were collected from fields in Nebraska, Missouri, Wisconsin, and Illinois. Collected plants were assessed for at-harvest weed seed retention in 2013 and 2014. Within 1 wk of soybean maturity,Amaranthusplants were harvested and the loose soil and debris beneath the plants were swept into a pan with a hand broom to collect any shattered seed. Percent seed retention ranged from 95 to 100% for all states both years, regardless of species. There was a strong correlation between weed biomass (g) and total seed production (no. plant−1) in that the larger the plant, the more seeds it produced. However, there was no correlation between percent seed retention and weed biomass, which indicates that regardless of plant size and likely time of emergence, seed retention is high at the time of crop maturity. Overall, this study demonstrated that there is great opportunity for Palmer amaranth and tall waterhemp seed capture or destruction at soybean harvest. It is likely that nearly all of the seeds produced for bothAmaranthusspecies passes through the combine during harvest to be returned to the soil seedbank. Thus, there is continued need for research focused on developing and testing harvest weed seed control tactics that aim at reducing the soil seedbank and lowering risks for evolution of herbicide resistance.

Response of pale swallowwort (Vincetoxicum rossicum) to multiple years of mowing

2019 ◽  
Vol 12 (03) ◽  
pp. 169-175
Author(s):  
Jeromy Biazzo ◽  
Lindsey R. Milbrath
Keyword(s):  
United States ◽  
Seed Production ◽  
Cropping Systems ◽  
Growing Season ◽  
Stem Density ◽  
Percent Cover ◽  
Mechanical Control ◽  
Vincetoxicum Rossicum ◽  
Crown Density ◽  
Broadleaf Species

AbstractPale swallowwort (Vincetoxicum rossicum), as well as its congener, black swallowwort (Vincetoxicum nigrum), is a European viny milkweed that has become invasive in natural areas and perennial cropping systems in the northeastern and midwestern United States and southeastern Canada. Mechanical control over 1 to 2 yr has not been effective, but studies of a longer duration are needed. We measured effects of mowing (no mowing or three or six times per growing season) on stem and root crown densities, percent cover, and follicle (seed pod) production of V. rossicum and percent cover of other vegetation over a 7-yr period. Stem density, root crown density, and percent cover of V. rossicum were reduced after 3 to 5 yr of mowing regardless of mowing frequency. Cover of other, mostly nonnative, broadleaf species increased. Follicle production was eliminated in all years of the study. In our environment, mowing three times at monthly intervals during the growing season can prevent seed production. However, mowing must occur for at least 3 yr to reduce, but not eliminate, stands of V. rossicum.

scholarly journals Effect of single or sequential POST herbicide applications on seed production and viability of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in dicamba- and glyphosate-resistant soybean

2021 ◽  
pp. 1-8
Author(s):  
Jose H. S. de Sanctis ◽  
Stevan Z. Knezevic ◽  
Vipan Kumar ◽  
Amit J. Jhala
Keyword(s):  
Seed Production ◽  
Field Experiments ◽  
Seed Viability ◽  
The United States ◽  
Palmer Amaranth ◽  
Growth Stages ◽  
Soybean Field ◽  
Amaranth Seed ◽  
Soil Seedbank ◽  
Reduced Density

Abstract Glyphosate-resistant (GR) Palmer amaranth is a troublesome weed that can emerge throughout the soybean growing season in Nebraska and several other regions of the United States. Late-emerging Palmer amaranth plants can produce seeds, thus replenishing the soil seedbank. The objectives of this study were to evaluate single or sequential applications of labeled POST herbicides such as acifluorfen, dicamba, a fomesafen and fluthiacet-methyl premix, glyphosate, and lactofen on GR Palmer amaranth control, density, biomass, seed production, and seed viability, as well as grain yield of dicamba- and glyphosate-resistant (DGR) soybean. Field experiments were conducted in a grower’s field infested with GR Palmer amaranth near Carleton, NE, in 2018 and 2019, with no PRE herbicide applied. Acifluorfen, dicamba, a premix of fomesafen and fluthiacet-methyl, glyphosate, or lactofen were applied POST in single or sequential applications between the V4 and R6 soybean growth stages, with timings based on product labels. Dicamba applied at V4 or in sequential applications at V4 followed by R1 or R3 controlled GR Palmer amaranth 91% to 100% at soybean harvest, reduced Palmer amaranth density to as low as 2 or fewer plants m−2, reduced seed production to 557 to 2,911 seeds per female plant, and resulted in the highest soybean yield during both years of the study. Sequential applications of acifluorfen, fomesafen and fluthiacet premix, or lactofen were not as effective as dicamba for GR Palmer amaranth control; however, they reduced seed production similar to dicamba. On the basis of the results of this study, we conclude that dicamba was effective for controlling GR Palmer amaranth and reduced density, biomass, and seed production without DGR soybean injury. Herbicides evaluated in this study had no effect on Palmer amaranth seed viability.

Stereo photo series for quantifying natural fuels. Volume XII: Post-hurricane fuels in forests of the Southeast United States.

2009 ◽  
Author(s):  
Robert E. Vihnanek ◽  
Cameron S. Balog ◽  
Clinton S. Wright ◽  
Roger D. Ottmar ◽  
Jeffrey W. Kelly
Keyword(s):  
United States ◽  
Southeast United States

scholarly journals Rattail fescue (Vulpia myuros) interference and seed production as affected by sowing time and crop density in winter wheat

Weed Science ◽  
2020 ◽  
pp. 1-10
Author(s):  
Muhammad Javaid Akhter ◽  
Per Kudsk ◽  
Solvejg Kopp Mathiassen ◽  
Bo Melander
Keyword(s):  
Winter Wheat ◽  
Grain Yield ◽  
Seed Production ◽  
Yield Components ◽  
Field Experiments ◽  
Growing Season ◽  
Sowing Time ◽  
Growing Seasons ◽  
Crop Density ◽  
Wide Range

Abstract Field experiments were conducted in the growing seasons of 2017 to 2018 and 2018 to 2019 to evaluate the competitive effects of rattail fescue [Vulpia myuros (L.) C.C. Gmel.] in winter wheat (Triticum aestivum L.) and to assess whether delayed crop sowing and increased crop density influence the emergence, competitiveness, and fecundity of V. myuros. Cumulative emergence showed the potential of V. myuros to emerge rapidly and under a wide range of climatic conditions with no effect of crop density and variable effects of sowing time between the two experiments. Grain yield and yield components were negatively affected by increasing V. myuros density. The relationship between grain yield and V. myuros density was not influenced by sowing time or by crop density, but crop–weed competition was strongly influenced by growing conditions. Due to very different weather conditions, grain yield reductions were lower in the growing season of 2017 to 2018 than in 2018 to 2019, with maximum grain yield losses of 22% and 50% in the two growing seasons, respectively. The yield components, number of crop ears per square meter, and 1,000-kernel weight were affected almost equally, reflecting that V. myuros’s competition with winter wheat occurred both early and late in the growing season. Seed production of V. myuros was suppressed by delaying sowing and increasing crop density. The impacts of delayed sowing and increasing crop density on seed production of V. myuros highlight the potential of these cultural weed control tactics in the long-term management programs of this species.

Characterization of non-methane hydrocarbons in the rural southeast United States

1997 ◽  
Vol 31 (23) ◽  
pp. 4017-4038 ◽  
Author(s):  
Lisa M. Hagerman ◽  
Viney P. Aneja ◽  
William A. Lonneman
Keyword(s):  
United States ◽  
Southeast United States

scholarly journals Seed production of barnyardgrass (Echinochloa crus-galli) in response to time of emergence in cotton and rice

2011 ◽  
Vol 150 (6) ◽  
pp. 717-724 ◽  
Author(s):  
M. V. BAGAVATHIANNAN ◽  
J. K. NORSWORTHY ◽  
K. L. SMITH ◽  
P. NEVE
Keyword(s):  
United States ◽  
Seed Production ◽  
Herbicide Resistance ◽  
Crop Production ◽  
Integrated Management ◽  
Resistance Management ◽  
Simulation Models ◽  
Effective Resistance ◽  
Southern United States

SUMMARYThe spread of herbicide resistance in barnyardgrass (Echinochloa crus-galli(L.) Beauv.) poses a serious threat to crop production in the southern United States. A thorough knowledge of the biology of barnyardgrass is fundamental for designing effective resistance-management programmes. In the present study, seed production of barnyardgrass in response to time of emergence was investigated in cotton and rice, respectively, in Fayetteville and Rohwer, Arkansas, over a 2-year period (2008–09). Barnyardgrass seed production was greater when seedlings emerged with the crop, but some seed production was observed even if seedlings emerged several weeks after crop emergence. Moreover, barnyardgrass seed production was highly variable across environments. When emerging with the crop (0 weeks after crop emergence (WAE)), barnyardgrass producedc. 35 500 and 16 500 seeds/plant in cotton, andc. 39 000 and 2900 seeds/plant in rice, in 2008 and 2009, respectively. Seed production was observed when seedlings emerged up to 5 WAE (2008) or 7 WAE (2009) in cotton and up to 5 WAE (2008, 2009) in rice; corresponding seed production wasc. 2500 and 1500 seeds/plant in cotton, andc. 14 700 and 110 seeds/plant in rice, in 2008 and 2009, respectively. The results suggest that cultural approaches that delay the emergence of barnyardgrass or approaches that make the associated crop more competitive will be useful in integrated management programmes. In the context of herbicide resistance management, it may be valuable to prevent seed return to the seedbank, irrespective of cohorts. The findings are vital for parameterizing herbicide resistance simulation models for barnyardgrass.

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