EFFECTS OF THE POTATO APHID MACROSIPHUM EUPHORBIAE (THOMAS) (HOMOPTERA: APHIDIDAE) ON OILSEED FLAX, AND STAGE-SPECIFIC THRESHOLDS FOR CONTROL

1995 ◽  
Vol 127 (2) ◽  
pp. 213-224 ◽  
Author(s):  
I.L. Wise ◽  
R.J. Lamb ◽  
E.O. Kenaschuk
Keyword(s):  
Yield Loss ◽  
Oil Quality ◽  
Field Studies ◽  
Macrosiphum Euphorbiae ◽  
Economic Threshold ◽  
Full Bloom ◽  
Potato Aphid ◽  
Economic Thresholds ◽  
Effective Use ◽  
And Control

AbstractThe potato aphid, Macrosiphum euphorbiae (Thomas), infests oilseed flax, Linum usitatissimum L., when the crop is flowering and developing seeds. Field studies in cages, open plots, and commercial fields showed that the aphid can cause yield losses of 20% or more, but reduces the weight of individual seeds only slightly and has no effect on oil quality. A single application of a foliar insecticide at full bloom or the green boll stage will control the potato aphid until harvest. The yield loss of flax is 0.021 t/ha per aphid per plant for crops sampled at full bloom and 0.008 t/ha per aphid per plant for crops sampled at the green boll stage. The economic threshold for the potato aphid in flax is three aphids per plant at full bloom and eight aphids per plant at the green boll stage, based on crop prices and control costs from 1990 to 1992. Aphids should be controlled as soon as the economic threshold is exceeded. If control is not warranted at full bloom, aphid densities should be assessed again at the green boll stage. The effective use of growth-stage-specific sampling and economic thresholds will maximize the benefits of insecticide use for producers and minimize unnecessary or ineffectively timed applications.

ECONOMIC THRESHOLD FOR PLANT BUGS, LYGUS SPP. (HETEROPTERA: MIRIDAE), IN CANOLA

1998 ◽  
Vol 130 (6) ◽  
pp. 825-836 ◽  
Author(s):  
I.L. Wise ◽  
R.J. Lamb
Keyword(s):  
Brassica Napus ◽  
Brassica Rapa ◽  
Chemical Control ◽  
Yield Loss ◽  
Field Studies ◽  
Single Application ◽  
Economic Threshold ◽  
Bud Formation ◽  
Economic Thresholds ◽  
And Control

AbstractPlant bugs in the genus Lygus infest canola (Brassica napus L. and Brassica rapa L.) when the crop is producing buds, flowers, and pods. Field studies in cages and open plots show that plant bugs can reduce yield by 20% or more, but have little effect on seed size. A single application of a foliar insecticide when the crop has finished flowering and is beginning to produce pods will prevent most or all of the yield loss. The yield loss of canola that can be prevented by control is 0.007 t/ha per plant bug per 10 sweeps sampled at the end of flowering or the beginning of pod formation. The yield loss that can be prevented by a later application drops to 0.005 t/ha. When precipitation is greater than 100 mm from the onset of bud formation to the end of flowering, the crop may partially compensate for plant bug damage. The economic threshold for control of plant bugs in canola at the end of flowering or at the beginning of pod formation is 15 plant bugs per 10 sweeps, based on crop prices and control costs from 1989 to 1992. If plant bugs are present but control is not warranted when most flowering is complete, plant bug densities should be assessed again 5–7 days later as pods develop, but at this stage the threshold is 20 plant bugs per 10 sweeps. The use of economic thresholds for chemical control of plant bugs will maximize seed yield and minimize unnecessary or ineffectively timed insecticide applications.

scholarly journals Modelling the Economics of Controlling Nodding Broomrape (Orobanche cernua) in Sunflower (Helianthus annuus)

Weed Science ◽  
1996 ◽  
Vol 44 (3) ◽  
pp. 591-595 ◽  
Author(s):  
L. García-Torres ◽  
M. Castejón-Muñoz ◽  
M. Jurado-Expósito ◽  
F. López-Granados
Keyword(s):  
Helianthus Annuus ◽  
Crop Yield ◽  
Treatment Cost ◽  
Yield Loss ◽  
Field Studies ◽  
Control Treatment ◽  
Yield Reduction ◽  
Economic Threshold ◽  
Economic Thresholds ◽  
Crop Yield Loss

Field studies were conducted at nine locations in southern Spain during 2 yr to develop models of nodding broomrape competition with sunflower and to establish economic thresholds. At each location, 30 to 35 small plots, each consisting of three sunflower plants, were chosen at random. The infection severity (BIS, no. of emerged broomrapes per sunflower plant) varied from 0 to 35. Plots were harvested at maturity to assess several sunflower and broomrape population variables. The percent sunflower yield reduction averaged over locations due to broomrape was estimated by the equation: % SYR = 1.7 x BIS (r2= 0.92). Crop yield loss per BIS unit increased with the expected yield and was estimated to be about 25, 50, and 75 kg ha−1for yields of 1000, 2000, and 3000 kg ha−1, respectively. A consistent relationship could be established between broomrape-infected sunflower yield, crop and broomrape biomass, and BIS parameters: SSYI= 0.2259 x PoBio/(1 + 0.0687 x BIS) (r2= 0.7820). The BIS economic threshold was about 1.5 and 3.5 for control treatment cost of $ 40 ha−1and potential yields of 2000 and 1000 kg ha−1, respectively.

Economic and interference threshold densities of quackgrass (Elytrigia repens) in potato (Solanum tuberosum)

Weed Science ◽  
1998 ◽  
Vol 46 (2) ◽  
pp. 176-180 ◽  
Author(s):  
Régis Baziramakenga ◽  
Gilles D. Leroux
Keyword(s):  
Yield Loss ◽  
Dry Weight ◽  
Field Studies ◽  
Potato Yield ◽  
Hyperbolic Function ◽  
Yield Losses ◽  
Economic Threshold ◽  
Elytrigia Repens ◽  
Shoot Number ◽  
Dry Biomass

Field studies were conducted in 1989 and 1990 at St-Augustin, Quebec, Canada, to determine the economic threshold density of quackgrass in potato. Potato yield losses due to quackgrass interference increased with quackgrass population density. Potato yield ranged from 33 to 73% in 1989, and from 19 to 44% in 1990. The relationship between potato yield losses and quackgrass densities was described by a rectangular hyperbolic function. Dry weight of quackgrass proved to be the best predictor of potato yield loss compared to shoot number. The interference thresholds for 10% potato yield loss amounted to 25 shoots m−2or 20 g total dry biomass m−2. The economic threshold varied between 0.04 and 2 shoots m−2or 0.0165 and 1.5 g total dry biomass m−2, depending on the variables considered.

Downy Brome (Bromus tectorum) Interference and Economic Thresholds in Winter Wheat (Triticum aestivum)

Weed Science ◽  
1990 ◽  
Vol 38 (3) ◽  
pp. 224-228 ◽  
Author(s):  
Phillip W. Stahlman ◽  
Stephen D. Miller
Keyword(s):  
Winter Wheat ◽  
Bromus Tectorum ◽  
Yield Loss ◽  
Wheat Yield ◽  
Dry Weight ◽  
Quadratic Equation ◽  
Downy Brome ◽  
Economic Threshold ◽  
Weed Density ◽  
Economic Thresholds

Densities up to 100 downy brome m2were established in winter wheat in southeastern Wyoming and west-central Kansas to quantify wheat yield loss from downy brome interference and to approximate economic threshold levels. A quadratic equation best described wheat yield loss as a function of weed density when downy brome emerged within 14 days after wheat emergence. Densities of 24, 40, and 65 downy brome m2reduced wheat yield by 10, 15, and 20%, respectively. Wheat yield was not reduced when downy brome emerged 21 or more days later than wheat. Economic thresholds varied with changes in downy brome density, cost of control, wheat price, and potential wheat yield. In a greenhouse experiment, dry weight of 72-day-old wheat plants grown in association with downy brome was not affected by the distance between the weeds and wheat, whereas downy brome plant dry weight increased with increasing distance between the weeds and wheat.

Impact of common ragweed (Ambrosia artemisiifolia) aggregation on economic thresholds in soybean

Weed Science ◽  
2003 ◽  
Vol 51 (6) ◽  
pp. 947-954 ◽  
Author(s):  
Michael J. Cowbrough ◽  
Ralph B. Brown ◽  
François J. Tardif
Keyword(s):  
Moisture Content ◽  
Field Experiments ◽  
Yield Loss ◽  
Ambrosia Artemisiifolia ◽  
Threshold Values ◽  
Economic Threshold ◽  
Common Ragweed ◽  
Economic Thresholds ◽  
Significant Difference ◽  
Loss Models

One approach to site-specific weed control is to map weeds within a field and then divide the field area into smaller grid units. The decision to apply a herbicide to individual grid units, or decision units, is made by using yield loss models to establish an economic threshold level. However, decision units often contain weed populations with aggregated distributions. Many yield loss models have not considered this because experiments dealing with weed–crop competition typically assume uniform weed distributions. Therefore, these models may overestimate yield losses. Field experiments conducted in 1999 and 2000 compared the effects of common ragweed having a uniform distribution vs. an aggregated distribution on soybean seed yield, moisture content, and dockage. Field experiment data were used to calculate and compare economic thresholds for both distributions. Economic thresholds that considered drying costs and dockage also were compared. There was no significant difference inIparameters (yield loss as density approaches zero) between the two ragweed distributions in either year. Seed moisture content and dockage increased with increasing common ragweed densities, but increases were not significant at the break-even yield loss level. Economic threshold values were similar for both distributions with differences between aggregated and uniform of 0.14 and 0.01 plants m−2in 1999 and 2000, respectively. The economic threshold values were reduced by 0.01 to 0.06 plants m−2when drying costs and dockage were considered.

Volunteer Barley Interference in Spring Wheat Grown in a Zero-Tillage System

Weed Science ◽  
2007 ◽  
Vol 55 (1) ◽  
pp. 70-74 ◽  
Author(s):  
John T. O'Donovan ◽  
K. Neil Harker ◽  
George W. Clayton ◽  
Linda M. Hall ◽  
Jason Cathcart ◽  
...  
Keyword(s):  
Spring Wheat ◽  
Field Experiments ◽  
Yield Loss ◽  
Wheat Yield ◽  
High Rate ◽  
Initial Slope ◽  
Threshold Values ◽  
Economic Threshold ◽  
Economic Thresholds ◽  
The Impact

There is no published information on the impact of volunteer barley on wheat yield loss or on the economics of controlling barley with a herbicide. With the registration of imazamox-resistant wheat, it is now possible to control volunteer barley in wheat. Thus, the likelihood of growing wheat in rotation with barley may increase. Field experiments were conducted in 2003 and 2004 at Beaverlodge, Lacombe, and Edmonton, AB, Canada, and Saskatoon, SK, Canada, to determine the impact of volunteer barley on yield of imazamox-resistant spring wheat seeded at relatively low (100 kg ha−1) and high (175 kg ha−1) rates. Barley was seeded at different densities to simulate volunteer barley infestations. Regression analysis indicated that wheat-plant density influenced the effects of volunteer barley interference on wheat yield loss, economic threshold values, and volunteer barley fecundity among locations and years. Economic thresholds varied from as few volunteer barley plants as 3 m−2at Beaverlodge in 2003 and 2004 to 48 m−2at Lacombe in 2003. In most cases, wheat yield loss and volunteer barley fecundity were lower and economic thresholds were higher when wheat was seeded at the higher rate. For example, averaged over both years at Beaverlodge initial slope values (percentage of wheat yield loss at low barley density) were 4.5 and 1.7%, and economic threshold values of volunteer barley plants were 3 m−2and 8 m−2at low and high wheat seeding rates, respectively. Results indicate that volunteer barley can be highly competitive in wheat, but yield losses and wheat seed contamination due to volunteer barley can be alleviated by seeding wheat at a relatively high rate.

scholarly journals Soybean yield loss and economic thresholds due to glyphosate resistant hairy fleabane interference

2018 ◽  
Vol 84 (0) ◽  
Author(s):  
Dirceu Agostinetto ◽  
Diecson Ruy Orsolin da Silva ◽  
Leandro Vargas
Keyword(s):  
Yield Loss ◽  
Development Stage ◽  
Control Measures ◽  
Economic Threshold ◽  
Economic Management ◽  
Soybean Yield ◽  
Weed Density ◽  
Economic Thresholds ◽  
Soybean Price ◽  
Hairy Fleabane

ABSTRACT: The interference of glyphosate resistant hairy fleabane (Conyza bonariensis) has caused yield losses in soybean crop. Knowledge of the economic threshold is an important aspect for the economic management of resistant weeds. Because of it, the interference of the glyphosate resistant hairy fleabane density on the soybean yield loss was evaluated, as well as to estimate the economic threshold. Two experiments were conducted to verify the effect of different weed densities on the yield of two soybean cultivars (BRS Estância and BMX Turbo). Weed density ranged from 0 to 124 plants m-2. The yield of the BRS Estância decreased by 1.4% to the increase of one single plant, while for the BMX Turbo the loss was 25.9%. Soybean yield and economic threshold were lower for the BMX Turbo cultivar compared to the cultivar BRS Estância, which can be attributed to the genotype, competitive ability, weed development stage and/or environment. Increases in crop yield expectation, soybean price and herbicide efficiency reduce the economic threshold, indicating that the adoption of control measures should be taken when the weed density is low. Due to the high cost of hairy fleabane control, it is only feasible at high densities.

scholarly journals Response of Soybean to Halosulfuron Herbicide

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
V. K. Nandula ◽  
D. H. Poston ◽  
K. N. Reddy ◽  
K. Whiting
Keyword(s):  
Growth Stage ◽  
Yield Loss ◽  
Field Studies ◽  
Glyphosate Resistance ◽  
Growth And Yield ◽  
Full Bloom ◽  
Target Movement ◽  
Resistance Trait ◽  
Soybean Plants ◽  
Effect On Yield

Recently, halosulfuron injury in soybean through off-target movement of halosulfuron when applied to rice fields has been reported. Sulfonylurea-tolerant (ST) soybean varieties have enhanced tolerance for sulfonylurea herbicides and might provide an option for mitigating injury to soybean from halosulfuron drift. Experiments were conducted to evaluate the effect of halosulfuron on growth and yield of selected soybean varieties with ST trait alone and stacked with glyphosate resistance trait. Soybean plants were treated with halosulfuron at 0, 0.0043, 0.0087, 0.017, 0.034, and 0.069 kg ai/ha rate at the V3 growth stage in the greenhouse and at 0.034 kg/ha rate (labeled use rate in rice) in the field studies. All soybean varieties containing the ST trait exhibited some halosulfuron injury, but survived the halosulfuron application in the greenhouse. In field studies, a single POST application of halosulfuron at 0.034 kg/ha to soybean at three-trifoliolate leaf stage or at full bloom stage resulted in halosulfuron injury to a certain extent regardless of ST trait. Halosulfuron did not have a significant effect on yield of ST varieties compared to their respective nontreated controls. Severe halosulfuron injury in two non-ST varieties resulted in yield loss.

Velvetleaf (Abutilon theophrasti) Competition and Economic Thresholds in Conventional- and No-Tillage Corn (Zea mays)

Weed Science ◽  
1995 ◽  
Vol 43 (1) ◽  
pp. 81-87 ◽  
Author(s):  
John Cardina ◽  
Emilie Regnier ◽  
Denise Sparrow
Keyword(s):  
Seed Production ◽  
Yield Loss ◽  
Conventional Tillage ◽  
Hyperbolic Function ◽  
Yield Reduction ◽  
Corn Yield ◽  
No Tillage ◽  
Economic Threshold ◽  
Growing Seasons ◽  
Economic Thresholds

Studies were conducted in conventional and no-tillage corn in 1990, 1991, and 1992 at Wooster, OH, to measure corn yield and velvetleaf seed production in response to density of early and late emerging velvetleaf, and to estimate economic thresholds. The percent reduction in corn yield fit a hyperbolic function over velvetleaf densities from 1 to 30 plants m2. The percent yield loss and velvetleaf seed production were higher in a warm, wet year (1990) than in a dry (1991) or cold, wet year (1992). The percent corn yield reduction was generally greater in no-tillage than in conventional tillage and from early rather than late emerging velvetleaf. Maximum velvetleaf seed production ranged from about 18,000 seeds m2for early emerging weeds in no-tillage in 1990 to 100 seeds m2for late emerging weeds in no-tillage in 1992. The single year economic threshold for early emerging velvetleaf ranged from 0.40 to 14.0 velvetleaf m2in conventional tillage and 0.13 to 3.13 in no-tillage. Economic thresholds that were predicted using yield goal information deviated from actual thresholds (using actual yields) for a given year by −43 to 30%. Single year economic thresholds were similar in both tillage treatments, but their value for management decisions is questionable due to variation among growing seasons and weed seed production from subthreshold populations.

Volunteer Glyphosate-Resistant Corn Interference and Control in Glyphosate-Resistant Sugarbeet

2012 ◽  
Vol 26 (2) ◽  
pp. 348-355 ◽  
Author(s):  
Andrew R. Kniss ◽  
Gustavo M. Sbatella ◽  
Robert G. Wilson
Keyword(s):  
Yield Loss ◽  
Pearson Correlation ◽  
Time Lag ◽  
Correlation Coefficients ◽  
Field Studies ◽  
Optimal Time ◽  
Limited Information ◽  
Control Volunteer ◽  
Volunteer Corn ◽  
And Control

Glyphosate-resistant (GR) sugarbeet is commonly grown in rotation with GR corn, but there is limited information relating to volunteer GR corn interference or control in GR sugarbeet. Field studies were conducted near Lingle, WY and Scottsbluff, NE in 2009 and 2010 to quantify sugarbeet yield loss in response to volunteer corn density and duration of interference, and determine appropriate control practices for use in GR sugarbeet. Hybrid corn resulted in a similar competitive effect on sugarbeet sucrose yield as clumps of F2volunteer corn. Clumps of volunteer corn were controlled 81% compared with 73% for individual plants. Linear regression indicated sucrose yield loss of 19% for each corn plant m−2up to 1.7 plants m−2at three of four experimental sites. Pearson correlation coefficients between percentage sucrose yield loss and proportion of sunlight reaching the top of the sugarbeet canopy ranged from −0.42 to −0.92. The duration of corn interference required to cause a 5% sucrose yield loss (YL5) ranged from 3.5 to 5.9 wk after sugarbeet emergence (WAE) for hand-weeding or herbicide removal, respectively, due to the length of time herbicide-treated volunteer corn continued to shade sugarbeet plants. Differences between herbicide and hand-removal methods were attributed to the time lag between when the treatments were applied and when the corn ceased to block light from the sugarbeet canopy. Sethoxydim generally provided less volunteer corn control compared with either quizalofop or clethodim, and control increased with the addition of an oil adjuvant. If a grower were to implement a volunteer corn control practice 3.5 WAE, economic sugarbeet yield loss would be avoided. In eastern Wyoming and western Nebraska, the sugarbeet crop will typically have between four to eight true leaves at 3.5 WAE, and therefore this would be an optimal time to control volunteer corn. If volunteer corn is being hand weeded, theYL5estimate will also increase, and thus the window of time to control volunteer corn would be wider.

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