Glyphosate-Resistant Horseweed (Conyza canadensis) in Mississippi

2004 ◽  
Vol 18 (3) ◽  
pp. 820-825 ◽  
Author(s):  
Clifford H. Koger ◽  
Daniel H. Poston ◽  
Robert M. Hayes ◽  
Robert F. Montgomery
Keyword(s):  
Growth Stage ◽  
Leaf Growth ◽  
Glyphosate Resistance ◽  
Plant Size ◽  
Growth Stages ◽  
Conyza Canadensis ◽  
Fold Level

Survival of horseweed in several glyphosate-tolerant cotton and soybean fields treated with glyphosate at recommended rates preplant and postemergence was observed in Mississippi and Tennessee in 2001 and 2002. Plants originating from seed collected from fields where horseweed escapes occurred in 2002 were grown in the greenhouse to the 5-leaf, 13- to 15-leaf, and 25- to 30-leaf growth stages and treated with the isopropylamine salt of glyphosate at 0, 0.025, 0.05, 0.1, 0.21, 0.42, 0.84, 1.68, 3.36, 6.72, and 13.44 kg ae/ha to determine if resistance to glyphosate existed in any biotype. All biotypes exhibited an 8- to 12-fold level of resistance to glyphosate when compared with a susceptible biotype. One resistant biotype from Mississippi was two- to fourfold more resistant than other resistant biotypes. Growth stage had little effect on level of glyphosate resistance. The glyphosate rate required to reduce biomass of glyphosate-resistant horseweed by 50% (GR50) increased from 0.14 to 2.2 kg/ha as plant size increased from the 5-leaf to 25- to 30-leaf growth stage. The GR50rate for the susceptible biotype increased from 0.02 to 0.2 kg/ha glyphosate. These results demonstrate that the difficult-to-control biotypes were resistant to glyphosate, that resistant biotypes could survive glyphosate rates of up to 6.72 kg/ha, and that plant size affected both resistant and susceptible biotypes in a similar manner.

Glyphosate-Resistant Horseweed (Conyza canadensis) Control with Dicamba in Alabama

2015 ◽  
Vol 29 (4) ◽  
pp. 633-640 ◽  
Author(s):  
Michael L. Flessner ◽  
J. Scott McElroy ◽  
James D. McCurdy ◽  
Jordan M. Toombs ◽  
Glenn R. Wehtje ◽  
...  
Keyword(s):  
Growth Stage ◽  
Resistance Management ◽  
Population Data ◽  
Glyphosate Resistance ◽  
Data Type ◽  
Growth Stages ◽  
Conyza Canadensis ◽  
Susceptible Population ◽  
Resistance Evaluation ◽  
Treatment Research

The development and spread of glyphosate-resistant (GR) horseweed has increased the use of dicamba as an alternative herbicide treatment. Research evaluated suspected glyphosate-resistant horseweed populations from DeKalb (GR-1) and Cherokee (GR-2) counties, Alabama, for response to glyphosate, dicamba, and glyphosate + dicamba. Populations used for resistance determination were tested at rosette and bolt growth stages. Glyphosate resistance evaluation treatments ranged from 0 to 36.0 kg ae ha−1. Data confirmed that GR-1 and GR-2 horseweed populations were 3.0 to 38 times more resistant to glyphosate than the susceptible population, according to population, data type, and growth stage at treatment. GR-1 and GR-2 populations were further evaluated for response to dicamba. Dicamba was applied at 0 to 1.12 kg ai ha−1, both with and without the addition of glyphosate at 1.12 kg ae ha−1. All populations had similar tolerance to dicamba, with the exception of GR-2 treated at the rosette growth stage, which had ~2-fold greater tolerance. When glyphosate was tank-mixed with dicamba, the response of GR populations was similar to that of dicamba alone. Therefore, any potential resistance-management benefit of tank-mixing dicamba with glyphosate may be negated when one is attempting to control GR horseweed. Conversely, adding glyphosate to dicamba drastically enhanced control of the susceptible population at both growth stages.

Clopyralid Dose Response for Two Black Medic (Medicago lupulina) Growth Stages

2016 ◽  
Vol 30 (3) ◽  
pp. 717-724 ◽  
Author(s):  
Shaun M. Sharpe ◽  
Nathan S. Boyd ◽  
Peter J. Dittmar
Keyword(s):  
Dose Response ◽  
Growth Stage ◽  
Plant Size ◽  
Stem Length ◽  
Effective Dosage ◽  
Growth Stages ◽  
Response Curves ◽  
Measured Range ◽  
Large Growth ◽  
Small Growth

Black medic is a troublesome weed in commercial strawberry fields in Florida. It emerges during crop establishment from the planting holes punched in plastic mulches that are installed on raised beds. Clopyralid is registered for posttransplant applications at 140 to 280 g ae ha−1but growers typically report suppression, not control. An outdoor potted experiment was designed to model the black medic dose-response curve and determine the effect of plant size at application on control. Two plant sizes were selected: designated small (0.5- to 1-cm stem length) and large (3- to 6-cm stem length). Dose-response curves were generated using a log-logistic four-parameter model. At 22 d after treatment (DAT), there was a significant interaction between clopyralid rate and black medic growth stage on both epinasty (P = 0.0022) and chlorosis (P = 0.0055). The effective dosage to induce 90% (ED90) epinasty were 249.5 and 398.3 g ha−1for the small and large growth stages, respectively. The ED90 for chlorosis was 748.2 for the small growth stage, whereas the estimated value for the large was outside the measured range. For necrosis there was no significant effect of growth stage, and the ED90 was 1,856.3 g ha−1. The aboveground dry biomass ED90 for the small growth stage was 197.3 g ha−1, and the estimated ED90 value for the large was not within the measured range. Results indicate that clopyralid adequately controls black medic when applied at maximum label rates when stems were 0.5 to 1 cm long but not when plants were larger. Poor efficacy typically observed in commercial fields is likely due to black medic plant size or lack of herbicide coverage via shielding by strawberry plants.

Safening Influence of LAB 145 138 on Nicosulfuron, Terbufos and Bentazon Interactions in Sweet Corn (Zea mays)

Weed Science ◽  
1996 ◽  
Vol 44 (2) ◽  
pp. 339-344 ◽  
Author(s):  
Darren K. Robinson ◽  
David W. Monks ◽  
James D. Burton
Keyword(s):  
Zea Mays ◽  
Seed Treatment ◽  
Growth Stage ◽  
Yield Loss ◽  
Sweet Corn ◽  
Leaf Growth ◽  
Growth Stages ◽  
Height Reduction ◽  
Reduced Height ◽  
Previously Treated

LAB 145 138 (LAB) was evaluated as a safener to improve sweet corn tolerance to nicosulfuron applied POST alone or with terbufos applied in the planting furrow or bentazon applied POST. To ensure enhanced injury for experimental purposes, nicosulfuron was applied at twice the registered rate alone or mixed with bentazon at the six- to seven-leaf growth stage of corn previously treated with the highest labeled rate of terbufos 15 G formulation. LAB applied as a seed treatment (ST) or POST at the two- to three-, four- to five-, or six- to seven-leaf growth stages reduced height reduction and yield loss from nicosulfuron applied POST in combination with terbufos applied in-furrow. LAB applied POST at the four- to five-leaf growth stage was most effective in preventing injury from this treatment, with yield reduced only 8% compared with 54% from the nicosulfuron and terbufos treatment. LAB applied POST at the eight- to nine-leaf growth stage did not alleviate injury. With the nicosulfuron, terbufos, and bentazon combination, LAB applied POST at the three- to four- or six- to seven-leaf growth stages decreased height reduction and yield loss caused by this combination, with LAB at the three- to four-leaf growth stage being most effective.

Control of Early Watergrass (Echinochloa Oryzoides) and Late Watergrass (Echinochloa Phyllopogon) with Cyhalofop, Clefoxydim, and Penoxsulam Applied Alone and in Mixture with Broadleaf Herbicides

2006 ◽  
Vol 20 (4) ◽  
pp. 992-998 ◽  
Author(s):  
Christos A. Damalas ◽  
Kico V. Dhima ◽  
Ilias G. Eleftherohorinos
Keyword(s):  
Growth Stage ◽  
Leaf Growth ◽  
Application Rate ◽  
Early Growth ◽  
Rice Fields ◽  
Growth Stages ◽  
Early Growth Stage ◽  
Late Growth ◽  
Echinochloa Phyllopogon

Experiments were conducted to study the effect of application rate, growth stage, and tank-mixing azimsulfuron or bentazon on the activity of cyhalofop, clefoxydim, and penoxsulam against two morphologically distinctEchinochloaspecies from rice fields in Greece. Mixtures of penoxsulam with MCPA were also evaluated. Cyhalofop (300 to 600 g ai/ha) applied at the three- to four-leaf growth stage provided 62 to 85% control of early watergrass but 41 to 83% control of late watergrass averaged over mixture treatments. Control ranged from 37 to 80% for early watergrass and from 35 to 78% for late watergrass when cyhalofop was applied at the five- to six-leaf growth stage averaged over mixture treatments. Mixtures of cyhalofop with azimsulfuron or bentazon reduced efficacy on both species irrespective of growth stage or cyhalofop application rate compared with cyhalofop alone. Clefoxydim (100 to 250 g ai/ha) applied alone at the three- to four-leaf growth stage provided 98 to 100% control of early watergrass and 91 to 100% control of late watergrass; when clefoxydim was applied alone at the five- to six-leaf growth stage the control obtained was 91 to 100% for early watergrass and 79 to 100% for late watergrass. Mixtures of clefoxydim with azimsulfuron or bentazon reduced efficacy on late watergrass at the early growth stage and on both species at the late growth stage. Penoxsulam (20 to 40 g ai/ha) applied alone provided 94 to 100% control of both species at both growth stages. Mixtures of MCPA with penoxsulam reduced efficacy on late watergrass at the early growth stage and on both species at the late growth stage. Mixtures of penoxsulam with azimsulfuron or bentazon reduced efficacy only on late watergrass at the late growth stage.

Relative effectiveness of various sources, methods, times and rates of copper fertilizers in improving grain yield of wheat on a Cu-deficient soil

2005 ◽  
Vol 85 (1) ◽  
pp. 59-65 ◽  
Author(s):  
S. S. Malhi ◽  
L. Cowell ◽  
H. R. Kutcher
Keyword(s):  
Grain Yield ◽  
Protein Concentration ◽  
Growth Stage ◽  
Foliar Application ◽  
Leaf Growth ◽  
Flag Leaf ◽  
Relative Effectiveness ◽  
Growing Season ◽  
Growth Stages ◽  
Cu Deficiency

A field experiment was conducted to determine the relative effectiveness of various sources, methods, times and rates of Cu fertilizers on grain yield, protein concentration in grain, concentration of Cu in grain and uptake of Cu in grain of wheat (Triticum aestivum L.), and residual concentration of DTPA-extractable Cu in soil on a Cu-deficient soil near Porcupine Plain in northeastern Saskatchewan. The experiment was conducted from 1999 to 2002 on the same site, but the results for 2002 were not presented because of very low grain yield due to drought in the growing season. The 25 treatments included soil application of four granular Cu fertilizers (Cu lignosulphonate, Cu sulphate, Cu oxysulphate I and Cu oxysulphate II) as soil-incorporated (at 0.5 and 2.0 kg Cu ha-1), seedrow-placed (at 0.25 and 1.0 kg Cu ha-1) and foliar application of four solution Cu fertilizers (Cu chelate-EDTA, Cu sequestered I, Cu sulphate/chelate and Cu sequestered II at 0.25 kg Cu ha-1) at the four-leaf and flag-leaf growth stages, plus a zero-Cu check. Soil was tilled only once to incorporate all designated Cu and blanket fertilizers into the soil a few days prior to seeding. Wheat plants in the zero-Cu treatment exhibited Cu deficiency in all years. For foliar application at the flag-leaf stage, grain yield increased with all four of the Cu fertilizers in 2000 and 2001, and in all but Cu sequestered II in 1999. Foliar application at the four-leaf growth stage of three Cu fertilizers (Cu chelate-EDTA, Cu sequestered I and Cu sulphate/chelate), soil incorporation of all Cu fertilizers at 2 kg Cu ha-1 and two Cu fertilizers (Cu lignosulphonate and Cu sulphate) at 0.5 kg Cu ha-1 rate, and seedrow placement of two Cu fertilizers (Cu lignosulphonate and Cu sulphate) at 1 kg Cu ha-1 increased grain yield of wheat only in 2001. There was no effect of Cu fertilization on protein concentration in grain. The increase in concentration and uptake of Cu in grain from Cu fertilization usually showed a trend similar to grain yield. There was some increase in residual DTPA-extractable Cu in the 0–60 cm soil in Cu lignosulphonate, Cu sulphate and Cu oxysulphate II soil incorporation treatments, particularly at the 2 kg Cu ha-1 rate. In summary, the results indicate that foliar application of Cu fertilizers at the flag-leaf growth stage can be used for immediate correction of Cu deficiency in wheat. Because Cu deficiency in crops often occurs in irregular patches within fields, foliar application may be the most practical and economical way to correct Cu deficiency during the growing season, as lower Cu rates can correct Cu deficiency. Key words: Application time, Cu source, foliar application, granular Cu, growth stage, placement method, rate of Cu, seedrow-placed Cu, soil incorporation

Absorption, Translocation, and Activity of CGA-136872, DPX-V9360, and Glyphosate in Rhizome Johnsongrass (Sorghum halepense)

Weed Science ◽  
1991 ◽  
Vol 39 (3) ◽  
pp. 354-357 ◽  
Author(s):  
Rolando F. Camacho ◽  
Loren J. Moshier
Keyword(s):  
Growth Stage ◽  
Leaf Growth ◽  
Sorghum Halepense ◽  
Growth Stages ◽  
Foliar Absorption ◽  
Treated Leaf

Rhizome johnsongrass grown in the greenhouse and treated with glyphosate at 1680 g ai ha−1at an early (3- to 4-leaf) or late (6- to 8-leaf) growth stage displayed injury within a week. Plants treated with CGA-136872 or DPX-V9360 at 40 g ai ha−1at both growth stages displayed injury 1 to 2 weeks later. CGA-136872 did not prevent regrowth at either growth stage. No regrowth occurred from DPX-V9360 or glyphosate-treated plants. Foliar absorption by greenhouse-grown plants within 24 h of application was greater with14C-glyphosate than with14C-DPX-V9360 or14C-CGA-136872. More14C-DPX-V9360 was absorbed than14C-CGA-136872. Growth stage influenced glyphosate absorption (more by younger plants) but not CGA-136872 or DPX-V9360 absorption. Translocation of the14C-CGA-136872 and14C-DPX-V9360 out of the treated leaf was less than 20% of the absorbed label and was less than glyphosate translocation. Growth stage of rhizome johnsongrass at the time of treatment had no effect on the distribution of radiolabeled herbicides within 24 h.

Effect of timing of propiconazole application on foliar disease and yield of irrigated spring wheat in Saskatchewan from 1990 to 1992

1994 ◽  
Vol 74 (1) ◽  
pp. 205-207 ◽  
Author(s):  
L. J. Duczek ◽  
L. L. Jones-Flory
Keyword(s):  
Spring Wheat ◽  
Growth Stage ◽  
Leaf Growth ◽  
Stem Elongation ◽  
Maximum Yield ◽  
Tan Spot ◽  
Optimal Time ◽  
Growth Stages ◽  
Foliar Disease ◽  
Yield Increase

Applications of propiconazole on spring wheat at various growth stages at Outlook, Saskatchewan showed that the optimal time to spray was between the extension of the flag leaf growth stage to the medium milk growth stage (G.S. 41–75). The maximum yield increase was about 10% on the soft white spring wheat, Fielder, compared to a 3% yield increase on the hard red spring wheat, Katepwa. The disease levels on penultimate leaves was reduced by spray applications between stem elongation and medium milk growth stages (G.S. 31–75). Most of the foliar disease was caused by Septoria spp. with S. nodorum being the most prevalent pathogen; Pyrenophora tritici-repentis was also present. Key words: Propiconazole, septoria leaf blotch, tan spot

scholarly journals Nitrogen Rate and Timing of Nitrogen Application in Poinsettia (Euphorbia pulcherrima Willd. Ex Klotz.)

HortScience ◽  
1994 ◽  
Vol 29 (11) ◽  
pp. 1309-1313 ◽  
Author(s):  
Mary Ann Rose ◽  
John W. White
Keyword(s):  
Leaf Area ◽  
Growth Stage ◽  
Floral Induction ◽  
Dry Weight ◽  
Plant Size ◽  
Growth Stages ◽  
N Availability ◽  
Regression Equations ◽  
Shoot Dry Weight ◽  
N Rates

`Celebrate 2' Poinsettias were grown for 8 weeks in a controlled-environment growth room until first signs of bract coloration. In growth stage I (GSI; weeks 1 through 4) low, medium, and high N rates (25, 75, and 125 mg N/liter, respectively) were applied by subirrigation (no leaching). Following floral induction [growth stage II (GSII), weeks 5 to 8], there were nine treatments: all possible combinations of the three N rates in GSI plus three rates (75, 125, and 175 mg N/liter) in GSII. Although >80% of shoot dry weight and >90% of total leaf area developed during growth GSII, reaching an acceptable plant size by week 8 depended on receiving adequate fertilization in growth GSI. In contrast, leaf chlorosis, noted in plants receiving the lowest rate in GSI, was rapidly reversed by increasing the N rate in GSII. Quadratic regression equations fitted to shoot dry weight and leaf area data predicted that using 125 mg N/liter in both growth stages gave maximum responses at week 8. However, using 75 mg N/liter in GSI and 125 mg N/liter in GSII also produced acceptable growth in poinsettias. Our results suggest that some growth restriction imposed by N availability during the first 4 weeks of growth may be acceptable and perhaps desirable to reduce growth regulator use and the environmental impact of overfertilization.

Postemergence Control of Annual Grasses and Corn (Zea mays) Tolerance Using DPX-79406

1996 ◽  
Vol 10 (2) ◽  
pp. 288-294 ◽  
Author(s):  
Clarence J. Swanton ◽  
Kevin Chandler ◽  
Monica J. Elmes ◽  
Stephen D. Murphy ◽  
Glenn W. Anderson
Keyword(s):  
Weed Control ◽  
Growth Stage ◽  
Field Experiments ◽  
Leaf Growth ◽  
Free Field ◽  
Effective Control ◽  
Controlled Environment ◽  
Growth Stages ◽  
Annual Grass ◽  
Green Foxtail

DPX-79406 was evaluated for POST annual grass weed control in both controlled environment and field experiments. In controlled environment experiments, green foxtail was most susceptible to DPX-79406; whereas yellow foxtail was least susceptible of the species evaluated. DPX-79406 at 12 g/ha completely controlled six leaf black-seeded proso millet, yellow foxtail, green foxtail, and barnyardgrass. In the field, DPX-79406 at 3.0 to 25.0 g/ha effectively controlled annual grass weeds without injury to three- to six-leaf corn. There was more variation in the effectiveness of DPX-79406 applied in the field. Early POST applications provided less weed control than the late application, especially for barnyardgrass, because of weeds emerging after application. As a result, higher doses were sometimes needed for effective control. In weed-free field trials at two sites in 1990 and 1991, corn tolerated doses up to 75 g/ha of DPX-79406 applied at the three- to six-leaf growth stage. However, doses as low as 18.8 g/ha applied at the six- to nine-leaf growth stage reduced grain yield. In 1991, corn tillering increases and height and yield reductions were related linearly to the dose of DPX-79406 applied during later growth stages. DPX-79406 should be applied early POST in order to avoid crop injury while providing effective weed control.

scholarly journals 452 Stand Reduction and Foliage Damage Reduce Yield of Onion for Dehydration

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 471E-472
Author(s):  
George H. Clough
Keyword(s):  
Growth Stage ◽  
Leaf Growth ◽  
Field Trials ◽  
Growth Stages ◽  
Leaf Stage ◽  
Plant Growth Stages ◽  
The Impact ◽  
Stage Yield ◽  
Different Growth Stages ◽  
Production Characteristics

Field trials were conducted at Hermiston, Ore., from 1995 through 1998 to determine the impact of stand loss and plant damage at different growth stages on yield of onions grown for dehydration. The experiment was a complete factorial with four replications. Stand reduction (0%, 20%, 40%, 60%, 80%) and foliage damage (0%, 25%, 50%, 75%, or 100%) treatments were applied at 3-, 6-, 9-, and 12-leaf onion growth stages. All average onion production characteristics decreased linearly as stand reduction increased (plant population decreased) at all plant growth stages except average bulb weight which increased as stand was reduced. Bulb weight was not changed by up to 100% foliage removal at the three-leaf stage of growth. At the 6- and 12-leaf stages, bulb weight was reduced when >50% of the foliage was removed. The most severe response occurred at the nine-leaf stage when bulb weights were reduced the most. At the three-leaf stage, yield was not affected by foliage damage. At the six-leaf growth stage, yield was reduced by 75% or more foliage loss, but at the 9- and 12-leaf stages, >50% foliage removal reduced expected yields. As with bulb weight, the impact of foliage removal on yield was most severe at the nine-leaf growth stage.

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