Showing papers in "Weed Science in 1979"
TL;DR: Several inorganic salts added to the spray solution reduced the herbicidal activity of glyphosate [N-(phosphonomethyl)glycine] in 93 to 374 L/ha distilled water killed test plants.
Abstract: Several inorganic salts added to the spray solution reduced the herbicidal activity of glyphosate [N-(phosphonomethyl)glycine]. Of the salts tested, iron and aluminum reduced herbicidal activity most. Reductions by calcium and zinc were moderately severe; by magnesium, moderate; by potassium and sodium, none. The reduction in phytotoxicity seems to be caused by cations, but factors other than valence also may be involved. Reduction in phytotoxicity was related to salt concentration and spray volume. Glyphosate at 0.84 kg/ha in 93 to 374 L/ha distilled water killed test plants. Tap water was an equally effective carrier at 93 and 187 L/ha volumes, but was significantly less effective at the 374 L/ha volume. Activity decreased as the molar concentration of CaCl2 increased to 0.01. Herbicidal activity was eliminated at 0.01 M and 374 L/ha; however, concentrations of CaCl2 exceeding 0.04 M reversed the trend and reacted similarly to a 0.005 M solution, which approximates the minimum hardness of most ground waters in Kansas.
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TL;DR: The infestations of leafy spurge and other weeds of economic importance in the Euphorbiaceae are out of control in some states, and biological control is mentioned as a possible solution to the problem.
Abstract: A survey was made in the United States to determine the extent of the infestations of leafy spurge (Euphorbia esula L) and other weeds of economic importance in the Euphorbiaceae From introductions about 100 yr ago, leafy spurge is now found in 458 counties in 26 states from coast to coast The infestations are out of control in some states, and biological control is mentioned as a possible solution to the problem
93 citations
TL;DR: In this article, a 2-yr study was conducted to determine the influence of early and late soybean [Glycine max (L.) Merr.] planting dates on the competitiveness of velvetleaf (Abutilon theophrasti Medic).
Abstract: A 2-yr study was conducted to determine the influence of early and late soybean [Glycine max (L.) Merr.] planting dates on the competitiveness of velvetleaf (Abutilon theophrasti Medic). Velvetleaf was planted at densities of one plant per 61 and 30 cm of row, and competition ranged from 4 weeks to full season. Soybean planting dates were mid-May and late-June. Velvetleaf emerging with soybeans in mid-May were twice as competitive as those emerging with soybeans planted in late-June. A density of one velvetleaf per 30 cm of row competing full season reduced soybean yields 27% for the early and only 14% for the late planting date. The competitive difference was due to the short-day photoperiodic response of velvetleaf. Although the early growth stages of soybeans are more competitive than those of velvetleaf, 10 weeks after emergence velvetleaf competition reduced soybean growth and development. Velvetleaf does not appear to be a potential major problem in Arkansas for soybeans planted in June due to its photoperiodic response and late season competitiveness. However, the weed could present problems for soybeans planted early, especially when an early maturing variety is used.
88 citations
TL;DR: In this paper, the seeds of 10 grass and 33 broadleaved weed species were examined for response to ethylene, and the results showed that the effects ranged from none to syntergistic with the applied ethylene.
Abstract: Germination of seeds of 10 grass and 33 broadleaved weed species was examined for response to ethylene. Germination was promoted in nine species, inhibited in two, and not affected in the remainder. Of the species promoted, common purslane (Portulaca oleracea L.), common lambsquarters (Chenopodium album L.), and several Amaranths, including redroot pigweed (Amaranthus retroflexus L.), were affected most. Transformation of phytochrome to the active form (Pfr) gave interactions that ranged from none to syntergistic with the applied ethylene. In subsequent tests seeds of purslane, redroot pigweed, and giant foxtail (Setaria faberi Herrm.), a species not responsive to ethylene, were examined for germination response to 14 low molecular weight hydrocarbon gases other than ethylene. Some stimulation by the olefins propylene and propadiene was found for purslane and pigweed. Propionaldehyde and butyraldehyde were slightly stimulatory to purslane only.
77 citations
TL;DR: Based on its growth responses to temperature, itchgrass would reach 75 to 100% of its maximum potential growth in the Gulf Coast states, the lower Midwest, the South Atlantic states, and the Southwest, and represents a serious potential weed problem in these regions.
Abstract: To estimate the potential growth and distribution of itchgrass (Rottboellia exaltata L f) in the United States, we grew the plant in 36 combinations of day and night temperatures in controlledenvironment greenhouses Day temperatures ranged from 17 to 32 C and night temperatures from 11 to 26 C Total dry weights, leaf areas, heights, and numbers of tillers were determined at 3, 31, and 58 days after emergence Mathematical growth analysis techniques were used to calculate net assimilation rates (NAR) and leaf area durations (LAD) Maximum dry matter production (the product of NAR and LAD) and maximum leaf area production occurred at 3 2/26 C Dry matter production and leaf area production were greatly reduced by day temperatures below 29 C and night temperatures below 23 C The retardation of dry matter production by low night temperature was due mainly to reductions in LAD rather than to reductions in NAR Low day temperatures reduced dry matter production through combined effects on LAD and NAR At the warmer day temperatures, tiller production increased with decreasing night temperature Flowering occurred at all day temperatures and at all night temperatures of 14 C or greater Based on its growth responses to temperature, itchgrass would reach 75 to 100% of its maximum potential growth in the Gulf Coast states, the lower Midwest, the South Atlantic states, and the Southwest Therefore, it represents a serious potential weed problem in these regions Additional index words Exotic weed, growth analysis
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TL;DR: In this paper, the critical period of weed interference in tomatoes was between 24 and 36 days after transplanting, and the yield of tomatoes was reduced significantly when only 5% of the weeds were allowed to remain in the plots longer than 21 days.
Abstract: Transplanted tomatoes (Lycopersicon esculentum Mill. ‘Springset’) kept weed free for 36 days after transplanting, or weeded from the 24th day after transplanting, gave yields equal to those that had been kept weed free throughout the growing season. Conversely, when weeds were allowed to remain in the crop for more than 24 days after transplanting, yields were progressively reduced. Therefore, the ‘critical period’ of weed interference in tomatoes was between 24 and 36 days after transplanting. The yield of tomatoes was reduced significantly when only 5% of the weeds were allowed to remain in the plots longer than 21 days after transplanting. Weed interference appeared to have little, if any, effect on tomato juice quality as measured by color, consistency, and flavor.
TL;DR: Three-hour dark incubation did not enhance inhibitor activity in the resistant-type thylakoid membranes, suggesting specific structural or configura- tional changes associated with the reactive site may account for the differences in Hill reaction inhibition between biotypes.
Abstract: Thylakoid membranes isolated from chloroplasts of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]-susceptible (S) and -resistant (R) biotypes of common groundsel (Senecio vulgaris L.) were assayed to determine the effect of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea], bromacil (5-bromo-3-sec-butyl-6-methyluracil) and several s-triazine herbicides on photosystem II (PSII) activity. Each herbicide inhibited photosynthetic electron transport on the reducing side of PSII in thylakoid membranes from the susceptible biotype. Thylakoids isolated from the resistant biotype were 60 to 3200 times more tolerant to the inhibitors than thylakoids from the susceptible biotype. Electrophoretic analysis revealed no differences in molecular weight of membrane polypeptides of either common groundsel biotype. Three-hour dark incubation did not enhance inhibitor activity in the resistant-type thylakoid membranes. Specific structural or configurational changes associated with the reactive site may account for the differences in Hill reaction inhibition between biotypes. A relationship between herbicide structure and Hill reaction activity is discussed.
TL;DR: In this article, a linear relationship between seed weight and germination percentage was found for Yellow Nutsedge (Cyperus esculentus L.) inflorescence, which produced an average of 1227 and 6685 flowers per inflorescence from eight California fields sampled during 1974, 1975, and 1976.
Abstract: Yellow nutsedge (Cyperus esculentus L.) produced an average of 1227 and 6685 flowers per inflorescence from eight California fields sampled during 1974, 1975, and 1976. Up to 17% of the flowers produced seeds and up to 78% of the seed germinated. There was a linear relationship between seed weight and germination percentage. Purple nutsedge (C. rotundus L.) averaged between 186 and 1354 flowers per inflorescence from three California fields sampled in 1974 and 1976. Only 43 purple nutsedge seed were collected and none germinated. Yellow nutsedge produced viable seed about 2 weeks after anthesis. A day/night temperature of 38/32 C was best for seed germination, especially when accompanied by a light period. Yellow nutsedge has potential to reproduce by seed, but probability of purple nutsedge reproducing by seed is low.
TL;DR: Competition of yellow nutsedge with corn with corn was evaluated in the field at various yellow nut- sedge densities over a 3-yr period, revealing an 8% yield reduction for every 100 shoots/M2 .
Abstract: Competition of yellow nutsedge (Cyperus esculentus L.) with corn (Zea mays L.) was evaluated in the field at various yellow nutsedge densities over a 3-yr period. A relationship between yellow nutsedge density (shoots/m2') and percentage yield reduction revealed an 8% yield reduction for every 100 shoots/M2 . Two 3-yr studies were conducted to determine the most effective combination of preplant- incorporated, postemergence, or postemergence-directed treatments for yellow nutsedge control in corn. The preplant incorporated treatments were alachlor 12-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilidel, EPTC (S-ethyl dipropylthiocarbamate), or nothing; postemergence treatments were bentazon (3-isopropyl-1H-2,1,3-benzothiadiazin-4) 3H- one 2,2-dioxidel, two cultivations, or nothing; and the postemergence- directed treatments were ametryn (2-(ethylamino)-4-(isopropylamino)- 6-(methylthio)-s-triazine) or nothing. One preplant-incorporated treat- ment of EPTC or alachlor prevented yield reductions from yellow nut- sedge competition. When no control was practiced, yields were reduced 17% in a moderate yellow nutsedge infestation (initially infested with 300 tubers/m2') and 41% in a heavy infestation (initially infested with 1200 tubers/M2 ). Yields were reduced 7 to 8% in the moderate infesta- tion when no preplant-incorporated treatments were used regardless of whether postemergence or postemergence-directed treatments were also used. After 1 yr, all control measures resulted in less tuber density than no control measures, but all control treatments had essentially similar tuber densities. After the second year,several herbicide treatments were as effective as hand weeding in reducing tuber density. At least 2 yr of effective control treatments were required to reduce tubers to 20% of the original density, and 3 yr of treatment to reduce the density to 15% of the original density. No combination of treatments, including hand weeding, eliminated tubers after 3 yr. Additional index words. Alachlor, bentazon, EPTC, cultural control, tuber, preplant incorporation.
TL;DR: It is postulate that leafy spurge exhibits allelopathic characteristics which may result from the incorporation of dead or decaying plant material in soil.
Abstract: The allelopathic potential of leafy spurge (Eupborbia esula L) was investigated in the field and greenhouse Reductions in frequency and density of quackgrass [Agropyron repens (L) Beauvl and common ragweed (Ambrosia artemisiifolia L) were noted where leafy spurge had high densities in the field Field soil samples taken from areas of moderate and high leafy spurge densities inhibited tomatoes (Lycopersicon esculentum Mill) in the greenhouse Growth of seedlings was inhibited up to 60% when leafy spurge leaves, roots, or litter were incorporated into soil, but surface applied leafy spurge litter had no effect Growth inhibition was demonstrated for crabgrass [Digitaria sanguinalis (L) Scopl and tomato when 01 to 10% (w/w) of leafy spurge leaves or roots were added to soil Based on these studies we postulate that leafy spurge exhibits allelopathic characteristics which may result from the incorporation of dead or decaying plant material in soil Additional index words Plant litter, tomato, crabgrass
TL;DR: The authors showed that metribuzin-3-14C [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] was absorbed, translocated, and metabolized by both metribusin-tolerant "Essex" and metrizin-sensitive "Coker 102" soybean cultivars [Glycine max (L.) Merr.].
Abstract: Metribuzin-3-14C [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] was absorbed, translocated, and metabolized by both metribuzin-tolerant ‘Essex’ and metribuzin-sensitive ‘Coker 102’ soybean cultivars [Glycine max (L.) Merr.]. After 48 h Coker 102 accumulated 40% greater metribuzin equivalents in the shoots than Essex, but Essex shoots contained only 29% as much unaltered metribuzin as Coker 102, 1.08 and 3.68 μg per g dry weight, respectively. Essex is resistant to metribuzin primarily owing to a capacity to rapidly detoxify metribuzin to DA [6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one], to at least seven unidentified metabolites which remained in the aqueous fraction, and to an insoluble fraction. The unidentified metabolites in the aqueous fraction constituted the major detoxified breakdown products in both cultivars.
TL;DR: In this paper, the authors calculate prospective costs before starting the biological control of a weed and show that a complete biological control program is likely to cost 18.8-23.7 scientist-years or currently $1.2 to 1.5 million and thus is only economic for use against major weeds.
Abstract: The purpose of the paper is to permit the calculation of prospective costs before starting the biological control of a weed. The cost of the Canadian program from its start in 1950 to the end of 1976 was tabulated in scientist-years by target weed, agent, and the type of study done. This information and international data on the number of agents required to control a weed were used to calculate expected costs. A complete biological control program is likely to cost 18.8–23.7 scientist-years or currently $1.2 to 1.5 million and thus is only economic for use against major weeds. However, it is often possible to capitalize on studies done elsewhere, and under these circumstances biological control may be economic for solving more minor weed problems.
TL;DR: The host range of an isolate of the fungal pathogen Alternaria macrospora from infected spurred anoda [Anoda cristata (L.) Schlecht] leaves was studied in the greenhouse and growth chamber as discussed by the authors.
Abstract: The host range of an isolate of the fungal pathogen Alternaria macrospora Zimmerman from infected spurred anoda [Anoda cristata (L.) Schlecht.] leaves was studied in the greenhouse and growth chamber. The fungus was inoculated to representative plants in the Malvaceae, Solanaceae, Leguminosae, and Gramineae families. Evidence of infection was limited to plants in the Malvaceae, with spurred anoda being the most susceptible species tested. Only negligible damage was incited on cotton (Gossypium hirsutum L. ‘Stoneville 213′) and long staple cotton (G. barbadense L. ‘Pima S–5′), hollyhock [Althaea rosea (L.) Cav.], okra (Hibiscus esculentus L. ‘Clemson spineless’), prickly sida (Sida spinosa L.), velvetleaf (Abutilon theophrasti Medic.), and Venice mallow (Hibiscus trionum L.). Disease symptoms induced in cotton by the spurred anoda isolate of A. macrospora were much less severe than those reported for other isolates of the fungus. Therefore, the spurred anoda isolate may be a specialized form of the fungus.
TL;DR: In this paper, the effect of glyphosate (N-(phosphonomethyl)glycine) on carbon dioxide levels, ethylene production, and cellulase activity was investigated.
Abstract: The effect of glyphosate (N-(phosphonomethyl)glycine) on carbon dioxide. (CO/sub 2/) levels, ethylene production, and cellulase activity was investigated. Production of ethylene increased within 12 h and CO/sub 2/ increased within 24 h when 12-day-old bean plants (Phaseolus vulgaris L. Red Kidney) were treated with 20 mM isopropylamine salt of glyphosate. The CO/sub 2/ cycled for 3 days and then increased around treated plants. Specific activity of cellulase was increased in debladed bean seedlings that had been retreated with 20 mM isopropylamine salt of glyphosate. Cellulase enhancement was detected 2 days after the pretreated plants were debladed. Glyphosate-enhanced ethylene production may have increased the cellulase activity. 24 references, 3 figures.