Prediction of Rice Yield Loss and Economic Threshold Level by Densities of Sagittaria trifolia and Bidens frondosa in Direct-seeding Flooded Rice

Pachnoda interrupta is one of the head-infesting insect pests of sunflower in Maiduguri. Two separate field experiment(one each for sowing date effect and threshold level) were conducted to investigate the influence of sowing date on damage and yield loss by P. interrupta on sunflower and the economic threshold level for its control in Maiduguri. The result for influence of sowing date experiment shows that percentage incidence of infestation was highly significant on sunflower sown on the 5th July than other planting date except that of 26th July. Significantly lower damage was recorded on sunflower sown on 19th July than those on the 5th and grain yield loss was also significantly higher on 26th July sowings than all other dates. The results for economic threshold level experiment indicated that 2.38 and 2.36 beetles/head were the economic threshold level for flowing and milky grain stage respectively and there was a 1:4.9 cost: benefit ratio/ ha. This means that there is a 20% return for every unit of inputs. The result implies that 19th of July is the best planting date to reduce infestations, damage and yield loss from P. interrupta in Maiduguri and artificial control measures should be initiated when there are 1.9 to 2.0 beetles/plant.

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Yield Loss and Economic Threshold Level of Soybean due to Leaf Roller (Apoderus cyaneus Hope) in Nepal

Nepal Agriculture Research Journal ◽

10.3126/narj.v6i0.3367 ◽

1970 ◽

Vol 6 ◽

pp. 73-77

Author(s):

Bishnu K Gyawali

Keyword(s):

Population Density ◽

Field Experiments ◽

Yield Loss ◽

Threshold Level ◽

Growth Stages ◽

Yield Losses ◽

Adult Beetle ◽

Economic Threshold ◽

Leaf Roller ◽

Research Journal

Yield loss in soybean due to leaf roller (Apoderus cyaneus Hope) was studied at Khumaltarduring 1985 and 1986 seasons. Field experiments were conducted during vegetative as well asreproductive stages of soybean. Rolled leaves of soybean with eggs, grubs and pupae werecollected from the field and reared in the laboratory for adults. Adults were introduced intonylon cages installed at the central rows of each plot just after germination of soybean. Insectswere maintained at population density of 25, 50 and 100 per m2density, the potential grain yield loss of cultivar, Ransom soybean in its vegetative andreproductive stages were 103 and 48 mg per day respectively from each adult of A. cyaneus.Percentages of yield losses were 36.2, 45.2, and 58.0 during vegetative and 37.5, 48.5 and 66.0during reproductive stages from the insect population of 25, 50 and 100, respectively which, wasnot in accordance with the level of two and four fold increased population density of insect.Yield reduction was higher (260 and 108 mg per day) from each adult beetle at lower populationlevel (25) in both vegetative and reproductive stages of soybean.Key words: Economic threshold level; leaf roller; physiological growth stages; yield lossDOI: 10.3126/narj.v6i0.3367Nepal Agriculture Research Journal Vol.6 2005 pp.73-77

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Control period and economic threshold level of glyphosate tolerant weeds in 2.4-D resistant soybean

Australian Journal of Crop Science ◽

10.21475/ajcs.21.15.02.p3085 ◽

2021 ◽

pp. 297-304

Author(s):

Eduardo Roncatto ◽

Arthur Arrobas Martins Barroso ◽

Juliana Calegarim ◽

Felipe Ridolfo Lucio ◽

Paulo Fernando Adami

Keyword(s):

Weed Control ◽

Weed Management ◽

Yield Loss ◽

Control Period ◽

Threshold Level ◽

Economic Threshold ◽

Weed Species ◽

Randomized Design ◽

Herbicide Use ◽

Linear Regressions

Weed densities, species, costs of control, crop value and interference periods should be considered for weed management. With this regard, three experiments were carried out to evaluate weed control periods and weed density in a new soybean cultivar. In ths first trial, control efficacy was measured by visual phytotoxicity of four weed species I. hederifolia, E. heterophylla, Conyza spp. and R. brasiliensis using four different herbicides with two doses each: glyphosate (720 and 1,440 g ea ha-1), 2.4-D (670 and 1,340 g ea ha-1), glufosinate (400 and 600 g ea ha-1) and glyphosate + 2.4-D (410 + 390 and 820 + 780 g ea ha-1). Herbicides were sprayed in an entirely randomized 4x8+1 factorial scheme with six repetitions. In the second experiment, 2,4-D-resistant soybean growth was measured under increasing densities of the same weeds (21 plants m² vs 21, 42, 84, 168 and 336 plants m²). This experiment was conducted under entirely randomized design with 25 treatments with four repetitions. Critical level of damage and economic threshold level of each weed species in soybean were measured using non-linear regressions. In a third experiment, weed with soybean were submitted to increasing periods of control and coexistence (7, 14, 21, 28, 35, 49 and 70 days after soybean emergence, plus two control treatments). Glufosinate and glyphosate+2.4-D (820 + 780 g ea ha-1) showed greater weed control than glyphosate alone (720 g ea ha-1). The yield loss of 0.85, 2.12, 5.71 and 34.24% were found for each weed of E. heterophylla, I. hederifolia, R. brasiliensis and Conyza spp., coexisting with soybean. There was a soybean grain yield loss of 50% in the weedy treatment. Soybean weed management should occur between 18thand 48th days after its emergence. Economic threshold level on soybean yield suggested is below one plant of Conyza spp. and R. brasiliensis per m-². The use of glufosinate and glyphosate+2,4-D provides a greater flexibility of herbicide use for farmers

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Rice Yield Loss and Economic Threshold Levels by Densities of Scirpus planiculmis and Lindernia dubia in Wet-Seeded Rice Paddy Fields

Korean Journal of Weed Science ◽

10.5660/kjws.2011.31.4.348 ◽

2011 ◽

Vol 31 (4) ◽

pp. 348-354 ◽

Cited By ~ 1

Author(s):

Oh-Do Kwon ◽

Kyu-Nam An ◽

Yeen Lee ◽

Seo-Ho Shin ◽

Heung-Gyu Park ◽

...

Keyword(s):

Yield Loss ◽

Rice Yield ◽

Rice Paddy ◽

Paddy Fields ◽

Economic Threshold ◽

Threshold Levels ◽

Rice Paddy Fields

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Economic threshold levels for Chilo partellus (Lepidoptera: Pyralidae) control on resistant and susceptible sorghum plants

Bulletin of Entomological Research ◽

10.1017/s0007485300036403 ◽

1997 ◽

Vol 87 (1) ◽

pp. 89-93 ◽

Cited By ~ 5

Author(s):

J. van den Berg ◽

G. D. J. van Rensburg ◽

M. C. van der Westhuizen

Keyword(s):

Chilo Partellus ◽

Yield Loss ◽

Threshold Level ◽

Field Trials ◽

Economic Injury Level ◽

Economic Threshold ◽

Insecticide Application ◽

Yield Increase ◽

Linear Relationships ◽

Economic Injury

AbstractThe effect of various infestation levels of Chilo partellus Swinhoe on resistant and susceptible sorghum genotypes was assessed under artificial infestation in two field trials, conducted over two seasons. In the first season, infestation levels were 0, 10, 20, 40, 60 and 80 larvae per 2 m plot row. In the second season, additional treatments of one and two larvae per plot were included. A series of all infestation levels on susceptible plants was also included with an insecticide application 5 days after inoculation. Non-linear relationships between infestation level and yield loss were observed. In susceptible plants, small increases in initial larval infestation levels resulted in sharp increases in yield loss. An opposite tendency was observed in resistant plants where a tolerant reaction at lower infestation levels was observed. Gain threshold (GT) value, indicating the yield increase necessary to compensate for control costs, economic injury level (EIL) and economic threshold level (ETL) at which control actions should be initiated were determined for each genotype. Insecticide application on susceptible plants resulted in a 10% reduction in yield loss. However, the yield was still less than that of unsprayed resistant plants. The GT values indicated that insecticide application was economically warranted at an ETL of 20% and 2% of plants with visible symptoms of whorl damage, for the resistant and susceptible genotypes respectively.

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Tolerance of Southern US Rice Cultivars to Benzobicyclon

Weed Technology ◽

10.1017/wet.2017.64 ◽

2017 ◽

Vol 31 (5) ◽

pp. 658-665

Author(s):

Mason L. Young ◽

Jason K. Norsworthy ◽

Robert C. Scott ◽

Lon T. Barber

Keyword(s):

Yield Loss ◽

Rice Yield ◽

Rice Production ◽

Severe Injury ◽

Rice Cultivars ◽

Visible Injury ◽

Tropical Japonica ◽

Southern Us ◽

Crop Injury ◽

Rough Rice

Benzobicyclon is the first 4-hydroxyphenylpyruvate dioxygenase-inhibiting herbicide pursued for commercial registration in U.S. rice production. A study was conducted in 2015 and 2016 to evaluate the response of eight rice cultivars to post-flood application timings of benzobicyclon at 494 g ai ha-1(proposed 2X rate). ‘Caffey’, ‘CL151’, ‘CLXL745’, ‘Jupiter’, ‘LaKast’, ‘Mermentau’, ‘Roy J’, and ‘XL753’ were evaluated in response to applications of benzobicyclon. The highest level of visible injury was observed in LaKast at 7% in 2015. No visible injury was detected among other cultivars either year at 2 weeks after treatment. In 2015 and 2016, no more than a four-day delay to reach 50% heading occurred across all cultivars. Rough rice yield was not affected by any of the post-flood application timings of benzobicyclon. A second study was conducted in 2016 at three locations throughout Arkansas to investigate the tolerance of 19tropical japonica(inbred and hybrid) and twoindicainbred cultivars to a premix containing benzobicyclon at 494 g ai ha-1and halosulfuron at 72 g ai ha-1 applied 1 week after flooding. Thetropical japonicacultivars have excellent crop safety to benzobicyclon while application to theindicacultivars, Rondo and Purple Marker, expressed severe phytotoxicity. Benzobicyclon caused less than a 2 d delay in heading to thejaponicacultivars. Rough rice yield of thetropical japonicacultivars was not affected by benzobicyclon while yields of bothindicacultivars were negatively affected. Benzobicyclon can safely be applied to drill-seededtropical japonicainbred and hybrid cultivars in a post-flood application without concerns for crop injury. Benzobicyclon should not be used onindicacultivars as it will cause severe injury, delayed heading, and yield loss.

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