A WEED SURVEY OF PEDIGREED ALFALFA SEED FIELDS IN MANITOBA

1986 ◽  
Vol 66 (2) ◽  
pp. 413-416 ◽  
Author(s):  
M. S. GOODWIN ◽  
I. N. MORRISON ◽  
A. G. THOMAS
Keyword(s):  
Mean Field ◽  
Abundant Species ◽  
Canada Thistle ◽  
Field Density ◽  
Wild Mustard ◽  
Polygonum Convolvulus ◽  
Alfalfa Seed ◽  
Crepis Tectorum ◽  
Sonchus Arvensis ◽  
Weed Survey

Weeds were counted in 77 pedigreed alfalfa (Medicago sativa L.) seed fields located throughout Manitoba. The five most abundant species were all perennials: quackgrass (Agropyron repens (L.) Beauv.), dandelion (Taraxacum officinale Weber), Canada thistle (Cirsium arvense (L.) Scop.), bluegrass (Poa spp.), and perennial sow-thistle (Sonchus arvensis L.). Quackgrass occurred in 65% of the fields with a mean field density of 23.4 culms m−2, the highest density of any of the species. The next four most abundant species were annuals with narrow-leaved hawk’s-beard (Crepis tectorum L.) having the highest mean field density for annual species at 2.9 plants m−2, although it occurred less frequently (30%) than the other three annuals, wild buckwheat (Polygonum convolvulus L.), wild mustard (Sinapsis arvensis L.) and wild oats (Avena fatua L.).Key words: Weed survey, alfalfa, quackgrass, narrow-leaved hawk’s-beard

Comparison of weed communities in Manitoba ecoregions and crops

2000 ◽  
Vol 80 (4) ◽  
pp. 963-972 ◽  
Author(s):  
R. C. Van Acker ◽  
A. G. Thomas ◽  
J. Y. Leeson ◽  
S. Z. Knezevic ◽  
B. L. Frick
Keyword(s):  
Weed Management ◽  
Amaranthus Retroflexus ◽  
Weed Species ◽  
Canada Thistle ◽  
Wild Mustard ◽  
Polygonum Convolvulus ◽  
Weed Communities ◽  
Green Foxtail ◽  
Poaceae Family ◽  
Weed Survey

In 1997, a weed survey was conducted during July and August in fields of wheat, barley, oat, canola and flax in Manitoba. Field selection was based on a stratified-random sampling methodology using ecodistricts as strata. Species in the Poaceae family were most commonly observed in the survey, followed by species in the Polygonaceae, Asteraceae and Brassicaceae families. The six most abundant weed species were green foxtail [Setaria viridis (L.) Beauv.], wild oats (Avena fatua L.), wild buckwheat (Polygonum convolvulus L.), Canada thistle (Cirsium arvense L.), redroot pigweed (Amaranthus retroflexus L.) and wild mustard (Sinapis arvensis L.). The survey highlighted significant differences between ecoregions and between crops in residual weed infestations. The weed community in the Boreal Transition ecoregion was dominated by seven species, whereas fields in the Aspen Parkland and Lake Manitoba Plain ecoregions were dominated by two species and the Interlake Plain ecoregion was dominated by only one species. Although significant differences were found between the weed communities in crops, they were not as great as differences between ecoregions. The Manitoba residual weed community in 1997 was very similar to that reported for 1978–1981 and 1986, suggesting that the same species should remain a focus for weed management. Key words: Weed survey, weed relative abundance, weed distributions, Manitoba ecoregions

A survey of the occurrence of seedling weeds in spring annual crops in Manitoba

1991 ◽  
Vol 71 (3) ◽  
pp. 811-820 ◽  
Author(s):  
A. G. Thomas ◽  
D. I. Donaghy
Keyword(s):  
Chenopodium Album ◽  
Abundant Species ◽  
Amaranthus Retroflexus ◽  
Canada Thistle ◽  
Perennial Weed ◽  
Wild Buckwheat ◽  
Annual Crops ◽  
Wild Oats ◽  
Wild Mustard ◽  
Green Foxtail

A floristic survey for weeds in spring annual crops throughout Manitoba from 1975 to 1978 indicated the occurrence of a total of 83 species in 654 fields. Field counts were done during June when the crop and weeds were in the seedling stage. In terms of total abundance, the 28 annual dicotyledonous weeds were found to be the most important group among the 50 species occurring in more than 1% of the fields. Wild buckwheat (Polygonum convolvulus L.), wild mustard (Sinapis arvensis L.), redroot pigweed (Amaranthus retroflexus L.), and lamb's-quarters (Chenopodium album L.) were the most widespread and abundant species in this group with mean densities from 9.6 to 16.2 plants m−2. The combined abundance of green foxtail (Setaria viridis L.), wild oats (Avena fatua L.), and barnyard grass (Echinochloa crusgalli (L.) Beauv.), the three major annual monocotyledonous weeds, was nearly equal to that of the annual dicotyledonous weed group. Green foxtail was the most abundant weed, occurring in 89% of the fields at mean densities of 270.5 plants m−2. Canada thistle (Cirsium arvense (L.) Scop.) and perennial sow-thistle (Sonchus arvensis L.) were the most abundant species in the biennial and perennial weed group and had mean densities of 4.4–4.8 plants m−2 in infested fields. Key words: Weed survey, green foxtail, wild oats, wild buckwheat, wild mustard, Canada thistle

Hydroxylation of 2,4-D in Several Weed Species

Weed Science ◽  
1971 ◽  
Vol 19 (5) ◽  
pp. 507-510 ◽  
Author(s):  
J. Fleeker ◽  
R. Steen
Keyword(s):  
Weed Species ◽  
Kochia Scoparia ◽  
Wild Mustard ◽  
Polygonum Convolvulus ◽  
Period 2 ◽  
Setaria Glauca ◽  
Sonchus Arvensis ◽  
Dichlorophenoxy Acetic Acid ◽  
Brassica Kaber ◽  
Predominant Product

Wild buckwheat (Polygonum convolvulus L.), leafy spurge (Euphorbia esula L.), yellow foxtail [Setaria glauca (L.) Beauv.], and wild oat (Avena fatua L.) hydroxylated, in a 7-day period, 2 to 7% of the (2,4-dichlorophenoxy)acetic acid-1-14C (2,4-D-1-14C) absorbed. Only a trace of hydroxylation products was detected in wild mustard [Brassica kaber (DC.) L. C. Wheeler var. pinnatifida (Stokes) L. C. Wheeler], perennial sowthistle (Sonchus arvensis L.), and kochia [Kochia scoparia (L.) Roth]. The investigation was limited to hydroxylation on the para-position of the herbicide. The predominant product, 2,5-dichloro-4-hydroxyphenoxyacetic acid, was detected in all weed species studied. Also found in measurable amounts in some species were 2,3-dichloro-4-hydroxyphenoxyacetic acid and 2-chloro-4-hydroxyphenoxyacetic acid. The hydroxylation rate on the number four carbon of the ring did not account for the variation in susceptibility exhibited by these plants.

Absorption, Translocation, and Foliar Activity of Clopyralid and Chlorsulfuron in Canada Thistle (Cirsium arvense) and Perennial Sowthistle (Sonchus arvensis)

Weed Science ◽  
1985 ◽  
Vol 33 (4) ◽  
pp. 524-530 ◽  
Author(s):  
Malcolm D. Devine ◽  
William H. Vanden Born
Keyword(s):  
Cirsium Arvense ◽  
Canada Thistle ◽  
Similar Treatment ◽  
Sonchus Arvensis ◽  
Root Buds

Both14C-clopyralid (3,6-dichloropicolinic acid) and14C-chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzensulfonamide} were readily absorbed by Canada thistle [Cirsium arvense(L.) Scop. ♯ CIRAR] leaves, with 99 and 75%, respectively, of the applied doses absorbed 144 h after application. Absorbed14C-clopyralid was rapidly exported from the treated leaves, whereas14C-chlorsulfuron was translocated much more slowly. After 144 h, 29% of the applied14C-clopyralid and 5% of the applied14C-chlorsulfuron were recovered in the roots and developing root buds of Canada thistle plants. Smaller amounts of the two herbicides were absorbed and translocated in perennial sowthistle (Sonchus arvensisL. ♯ SONAR) than in Canada thistle. More14C-clopyralid than14C-chlorsulfuron was absorbed and translocated out of treated leaves of perennial sowthistle, but equal amounts, 3 to 4% of the applied doses, were recovered in the roots and root buds 144 h after application. Foliar applications of clopyralid, followed by removal of the treated shoot 24, 72, or 144 h after application, markedly reduced shoot regrowth in both Canada thistle and perennial sowthistle. Similar treatment with chlorsulfuron did not prevent shoot regrowth in either species.

Preharvest glyphosate in alfalfa for seed production: Effect on alfalfa seed yield and quality

2003 ◽  
Vol 83 (1) ◽  
pp. 189-197 ◽  
Author(s):  
W. E. May ◽  
H. A. Loeppky ◽  
D. C. Murrell ◽  
C. D. Myhre ◽  
J. J. Soroka
Keyword(s):  
Seed Production ◽  
Seed Yield ◽  
Seed Quality ◽  
Seedling Emergence ◽  
Canada Thistle ◽  
Seedling Vigour ◽  
Yield And Quality ◽  
Alfalfa Seed ◽  
Medicago Sativa L ◽  
Seed Yields

Preharvest applications of glyphosate have been shown to be effective in controlling Canada thistle in annual crops, but may reduce alfalfa seed yield depending on time and rate of application. The objective of this study was to determine the effect of preharvest applications of glyphosate on subsequent alfalfa seed yield and quality. The effects of timing, 1, 26, 51 and 76% alfalfa seed pod maturity, and rate, 0, 440, 880, 1320, and 1760 g a.i. ha-1, of a preharvest application of glyphosate on alfalfa seed yield and quality in the year of application, and regrowth and seed yield in the following year were determined. The rate of glyphosate applied did not affect seed yield in the application year; however, in the following year, growth and seed yield were reduced as rates increased. Delaying the application of glyphosate increased seed yields in the application year, but decreased alfalfa regrowth and flowering the following year. Germination and seedling emergence were not affected by the rate or timing of the glyphosate. A preharvest application of glyphosate at 1760 g a.i. ha-1 at 76% pod maturity is a viable option in the last year of seed production. Key words: Alfalfa (Medicago sativa L.), glyphosate, abnormal seeds, seed quality, and seedling vigour

Weed Survey System used in Saskatchewan for Cereal and Oilseed Crops

Weed Science ◽  
1985 ◽  
Vol 33 (1) ◽  
pp. 34-43 ◽  
Author(s):  
A. Gordon Thomas
Keyword(s):  
Growing Season ◽  
Agricultural Extension ◽  
Sampling Procedure ◽  
Distribution Maps ◽  
Agricultural Extension Service ◽  
Polygonum Convolvulus ◽  
Green Foxtail ◽  
Survey System ◽  
Weed Survey

A weed survey system methodology was developed and used annually for 4 yr in the province of Saskatchewan. Based on a stratified random sampling procedure, fields were selected in wheat (Triticum aestivumL.), barley (Hordeum vulgareL.), oat (Avena sativaL.), rye (Secale cerealeL.), rape (Brassica napusL.,Brassica campestrisL.), and flax (Linum usitatissimumL.) crops. The boundaries of the 43 agricultural extension districts in the province formed the strata. The provincial agricultural extension service provided staff to conduct the survey. Computer processing of the data enabled reports, containing summary tables and distribution maps, to be distributed to extension, research, and industry personnel within 3 months after completion of the field survey. The field surveys were conducted late in the growing season before harvest commenced; hence, the weed populations consisted of species that had been present during the early part of the growing season and may have contributed to yield losses. During the 4 yr of the survey, weeds were counted in 4423 fields. Of the 164 species recorded, 97 species occurred in more than three fields. Only 29 species were encountered frequently in the fields. Green foxtail [Setaria viridis(L.) Beauv. # SETVI), wild buckwheat (Polygonum convolvulusL. # POLCO), and wild oat (Avena fatuaL. # AVEFA) were the top three species based on a ranking system using a measure called relative abundance.

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