The Experts below are selected from a list of 1569 Experts worldwide ranked by ideXlab platform
Ravi Naidu - One of the best experts on this subject based on the ideXlab platform.
-
Purification and characterization of a novel Fenamiphos hydrolysing enzyme from Microbacterium esteraromaticum MM1.
Chemosphere, 2020Co-Authors: Panneerselvan Logeshwaran, Ravi Naidu, Kannan M. Krishnan, Mallavarapu MegharajAbstract:Abstract Fenamiphos is a neurotoxic organophosphorus pesticide used widely to control pests of crops. Fenamiphos and its toxic oxidation products have been detected in surface and groundwaters. A novel enzyme capable of hydrolysing P–O–C bond of Fenamiphos is purified from Microbacterium esteraromaticum MM1 total cellular protein using a combination of methods. The purified Fenamiphos hydrolysing enzyme (FHE) was identified as enolase (phosphopyruvate hydratase), a housekeeping enzyme with molecular mass and pI value of 45 kDa and 4.5, respectively. The optimum pH and temperature for the activity of the FHE are 7 and 25 °C, respectively. We studied the influence of metal ions and inhibitors on the enzyme activity. The enzyme was strongly activated by Mg2+ whereas Hg2+ and phenylmethyl sulfonyl fluoride (PMSF) inhibited the enzyme. The kinetic parameters, Km and Vmax for Fenamiphos hydrolysis were estimated to be 584.15 ± 16.22 μM and 6.46 ± 0.13 μM min−1, respectively. The FHE was functionally active against its original substrate (2-phosphoglycerate) with Km value of 5.82 ± 1.42 μM and Vmax of 4.2 ± 0.1 μM min−1. This enzyme has great potential for its application in the detoxification of Fenamiphos and its warfare homologs. To our knowledge, this is the first report on the purification of Fenamiphos hydrolysing enzyme.
-
Toxicity and transformation of insecticide Fenamiphos to the earthworm Eisenia fetida
Ecotoxicology, 2011Co-Authors: Tanya P. Cáceres, Mallavarapu Megharaj, Ravi NaiduAbstract:This study was conducted to investigate the toxicity of the organophosphate insecticide Fenamiphos to earthworms ( Eisenia fetida ) under laboratory conditions. Earthworms were exposed to soils differing in their physico-chemical properties spiked with Fenamiphos at concentrations ranging from 10 to 200 mg kg^−1 for a period of 4 weeks. Residues of Fenamiphos and its metabolites were determined in both soils and earthworms after 4 weeks of pesticide exposure. Fenamiphos was degraded faster in the alkaline soil than in the neutral and acidic soils. Median lethal concentration of Fenamiphos in the neutral soil was 228 mg kg^−1 soil. Residues of Fenamiphos caused a significant reduction in the biomass of worms, especially the ones exposed to the pesticide in the acidic soil. In vitro experiments suggested that Fenamiphos was biotransformed in the earthworms principally to its oxide metabolite. To our knowledge, this is the first study demonstrating the biotransformation of Fenamiphos by E. fetida .
-
Hydrolysis of Fenamiphos and its toxic oxidation products by Microbacterium sp. in pure culture and groundwater.
Bioresource technology, 2009Co-Authors: Tanya Cáceres, Mallavarapu Megharaj, Seidu Malik, Michael Beer, Ravi NaiduAbstract:A bacterium with an exceptional ability to hydrolyse Fenamiphos and its toxic oxidation products Fenamiphos sulfoxide and Fenamiphos sulfone, all possessing POC bond was isolated from soil. Based on 16S rRNA gene determination, this bacterium was putatively identified as Microbacterium esteraromaticum. The phenols (Fenamiphos phenol, sulfoxide phenol and sulfone phenol) formed during bacterial hydrolysis resisted further degradation in mineral salts medium and sterile groundwater, but were transitory in non-sterile groundwater due to the catabolism of native microorganisms. Also, the cell-free preparation of this bacterium was highly effective in hydrolysing Fenamiphos and its oxides. These results demonstrate the potential of this bacterium to detoxify pesticide waste in the environment including the groundwater.
-
Effect of insecticide Fenamiphos on soil microbial activities in Australian and Ecuadorean soils.
Journal of environmental science and health. Part. B Pesticides food contaminants and agricultural wastes, 2008Co-Authors: Tanya Cáceres, Mallavarapu Megharaj, Ravi NaiduAbstract:The effect of Fenamiphos, a widely used organophosphorus pesticide, on important soil microbial activities such as dehydrogenase, urease and potential nitrification in four soils from Australia and Ecuador were studied. The results showed Fenamiphos in general was not toxic to dehydrogenase and urease up to 100 mg/Kg soil. However potential nitrification was found to be highly sensitive to Fenamiphos with a significant inhibition recorded even at 10 mg/Kg soil. In general, the nitrification activity in soils was decreased with an increase in Fenamiphos concentration. The calculated EC50 values for nitrification in all the tested soils ranged between 19 and 56 mg Fenamiphos/kg dry soil. This study suggests that Fenamiphos is likely to be detrimental to nitrification at field application rates.
-
Biodegradation of the Pesticide Fenamiphos by Ten Different Species of Green Algae and Cyanobacteria
Current microbiology, 2008Co-Authors: Tanya Cáceres, Mallavarapu Megharaj, Ravi NaiduAbstract:The degradation of an organophosphorus pesticide, Fenamiphos, by different species of five green algae and five cyanobacteria was studied. All the species tested were able to transform Fenamiphos to its primary oxidation product, Fenamiphos sulfoxide (FSO), while the majority of these cultures were able to hydrolyze FSO to Fenamiphos sulfoxide phenol (FSOP). Fenamiphos sulfone phenol, FSOP, and FSO were detected in the culture extracts of these algae and cyanobacteria. This is the first report on the biodegradation of a toxic pesticide, Fenamiphos, by cyanobacteria. The ability of these algae and cyanobacteria to detoxify Fenamiphos can be gainfully used in bioremediation of this pesticide and its toxic metabolites.
Mallavarapu Megharaj - One of the best experts on this subject based on the ideXlab platform.
-
Purification and characterization of a novel Fenamiphos hydrolysing enzyme from Microbacterium esteraromaticum MM1.
Chemosphere, 2020Co-Authors: Panneerselvan Logeshwaran, Ravi Naidu, Kannan M. Krishnan, Mallavarapu MegharajAbstract:Abstract Fenamiphos is a neurotoxic organophosphorus pesticide used widely to control pests of crops. Fenamiphos and its toxic oxidation products have been detected in surface and groundwaters. A novel enzyme capable of hydrolysing P–O–C bond of Fenamiphos is purified from Microbacterium esteraromaticum MM1 total cellular protein using a combination of methods. The purified Fenamiphos hydrolysing enzyme (FHE) was identified as enolase (phosphopyruvate hydratase), a housekeeping enzyme with molecular mass and pI value of 45 kDa and 4.5, respectively. The optimum pH and temperature for the activity of the FHE are 7 and 25 °C, respectively. We studied the influence of metal ions and inhibitors on the enzyme activity. The enzyme was strongly activated by Mg2+ whereas Hg2+ and phenylmethyl sulfonyl fluoride (PMSF) inhibited the enzyme. The kinetic parameters, Km and Vmax for Fenamiphos hydrolysis were estimated to be 584.15 ± 16.22 μM and 6.46 ± 0.13 μM min−1, respectively. The FHE was functionally active against its original substrate (2-phosphoglycerate) with Km value of 5.82 ± 1.42 μM and Vmax of 4.2 ± 0.1 μM min−1. This enzyme has great potential for its application in the detoxification of Fenamiphos and its warfare homologs. To our knowledge, this is the first report on the purification of Fenamiphos hydrolysing enzyme.
-
Toxicity and transformation of insecticide Fenamiphos to the earthworm Eisenia fetida
Ecotoxicology, 2011Co-Authors: Tanya P. Cáceres, Mallavarapu Megharaj, Ravi NaiduAbstract:This study was conducted to investigate the toxicity of the organophosphate insecticide Fenamiphos to earthworms ( Eisenia fetida ) under laboratory conditions. Earthworms were exposed to soils differing in their physico-chemical properties spiked with Fenamiphos at concentrations ranging from 10 to 200 mg kg^−1 for a period of 4 weeks. Residues of Fenamiphos and its metabolites were determined in both soils and earthworms after 4 weeks of pesticide exposure. Fenamiphos was degraded faster in the alkaline soil than in the neutral and acidic soils. Median lethal concentration of Fenamiphos in the neutral soil was 228 mg kg^−1 soil. Residues of Fenamiphos caused a significant reduction in the biomass of worms, especially the ones exposed to the pesticide in the acidic soil. In vitro experiments suggested that Fenamiphos was biotransformed in the earthworms principally to its oxide metabolite. To our knowledge, this is the first study demonstrating the biotransformation of Fenamiphos by E. fetida .
-
Hydrolysis of Fenamiphos and its toxic oxidation products by Microbacterium sp. in pure culture and groundwater.
Bioresource technology, 2009Co-Authors: Tanya Cáceres, Mallavarapu Megharaj, Seidu Malik, Michael Beer, Ravi NaiduAbstract:A bacterium with an exceptional ability to hydrolyse Fenamiphos and its toxic oxidation products Fenamiphos sulfoxide and Fenamiphos sulfone, all possessing POC bond was isolated from soil. Based on 16S rRNA gene determination, this bacterium was putatively identified as Microbacterium esteraromaticum. The phenols (Fenamiphos phenol, sulfoxide phenol and sulfone phenol) formed during bacterial hydrolysis resisted further degradation in mineral salts medium and sterile groundwater, but were transitory in non-sterile groundwater due to the catabolism of native microorganisms. Also, the cell-free preparation of this bacterium was highly effective in hydrolysing Fenamiphos and its oxides. These results demonstrate the potential of this bacterium to detoxify pesticide waste in the environment including the groundwater.
-
Effect of insecticide Fenamiphos on soil microbial activities in Australian and Ecuadorean soils.
Journal of environmental science and health. Part. B Pesticides food contaminants and agricultural wastes, 2008Co-Authors: Tanya Cáceres, Mallavarapu Megharaj, Ravi NaiduAbstract:The effect of Fenamiphos, a widely used organophosphorus pesticide, on important soil microbial activities such as dehydrogenase, urease and potential nitrification in four soils from Australia and Ecuador were studied. The results showed Fenamiphos in general was not toxic to dehydrogenase and urease up to 100 mg/Kg soil. However potential nitrification was found to be highly sensitive to Fenamiphos with a significant inhibition recorded even at 10 mg/Kg soil. In general, the nitrification activity in soils was decreased with an increase in Fenamiphos concentration. The calculated EC50 values for nitrification in all the tested soils ranged between 19 and 56 mg Fenamiphos/kg dry soil. This study suggests that Fenamiphos is likely to be detrimental to nitrification at field application rates.
-
Biodegradation of the Pesticide Fenamiphos by Ten Different Species of Green Algae and Cyanobacteria
Current microbiology, 2008Co-Authors: Tanya Cáceres, Mallavarapu Megharaj, Ravi NaiduAbstract:The degradation of an organophosphorus pesticide, Fenamiphos, by different species of five green algae and five cyanobacteria was studied. All the species tested were able to transform Fenamiphos to its primary oxidation product, Fenamiphos sulfoxide (FSO), while the majority of these cultures were able to hydrolyze FSO to Fenamiphos sulfoxide phenol (FSOP). Fenamiphos sulfone phenol, FSOP, and FSO were detected in the culture extracts of these algae and cyanobacteria. This is the first report on the biodegradation of a toxic pesticide, Fenamiphos, by cyanobacteria. The ability of these algae and cyanobacteria to detoxify Fenamiphos can be gainfully used in bioremediation of this pesticide and its toxic metabolites.
Tanya Cáceres - One of the best experts on this subject based on the ideXlab platform.
-
Sorption and mobility of 14 C-Fenamiphos in Brazilian soils.
Environmental monitoring and assessment, 2018Co-Authors: Tanya Cáceres, Kadiyala VenkateswarluAbstract:Although Fenamiphos is widely used as an insecticide and nematicide in bowling greens and agriculture, information on its sorption in tropical soils is limited. In this study, mobility, sorption, and desorption dynamics of 14C-Fenamiphos in three contrasting Brazilian soils were examined both in batch and column experiments. Fenamiphos sorption coefficients (K d ) were 2.33, 3.86, and 3.9 L kg−1 for the three soils tested. The insecticide exhibited linear adsorption isotherms in all the three soils, and desorption was in a range of 30–40% during a 72-h period. With its low mobility, Fenamiphos did not percolate through the soil profile even after 48 h. However, there is a risk of leaching to water bodies due to runoff because of its high solubility in water. In view of the fact that Fenamiphos and its oxidation products are highly toxic to aquatic invertebrates and could affect the soil microbial activities even at low concentrations, the present information is of great importance in risk assessment of Fenamiphos in the environment.
-
Sorption and mobility of ^14C-Fenamiphos in Brazilian soils
Environmental Monitoring and Assessment, 2018Co-Authors: Tanya Cáceres, Kadiyala VenkateswarluAbstract:Although Fenamiphos is widely used as an insecticide and nematicide in bowling greens and agriculture, information on its sorption in tropical soils is limited. In this study, mobility, sorption, and desorption dynamics of ^14C-Fenamiphos in three contrasting Brazilian soils were examined both in batch and column experiments. Fenamiphos sorption coefficients ( K _ d ) were 2.33, 3.86, and 3.9 L kg^−1 for the three soils tested. The insecticide exhibited linear adsorption isotherms in all the three soils, and desorption was in a range of 30–40% during a 72-h period. With its low mobility, Fenamiphos did not percolate through the soil profile even after 48 h. However, there is a risk of leaching to water bodies due to runoff because of its high solubility in water. In view of the fact that Fenamiphos and its oxidation products are highly toxic to aquatic invertebrates and could affect the soil microbial activities even at low concentrations, the present information is of great importance in risk assessment of Fenamiphos in the environment.
-
Hydrolysis of Fenamiphos and its toxic oxidation products by Microbacterium sp. in pure culture and groundwater.
Bioresource technology, 2009Co-Authors: Tanya Cáceres, Mallavarapu Megharaj, Seidu Malik, Michael Beer, Ravi NaiduAbstract:A bacterium with an exceptional ability to hydrolyse Fenamiphos and its toxic oxidation products Fenamiphos sulfoxide and Fenamiphos sulfone, all possessing POC bond was isolated from soil. Based on 16S rRNA gene determination, this bacterium was putatively identified as Microbacterium esteraromaticum. The phenols (Fenamiphos phenol, sulfoxide phenol and sulfone phenol) formed during bacterial hydrolysis resisted further degradation in mineral salts medium and sterile groundwater, but were transitory in non-sterile groundwater due to the catabolism of native microorganisms. Also, the cell-free preparation of this bacterium was highly effective in hydrolysing Fenamiphos and its oxides. These results demonstrate the potential of this bacterium to detoxify pesticide waste in the environment including the groundwater.
-
Effect of insecticide Fenamiphos on soil microbial activities in Australian and Ecuadorean soils.
Journal of environmental science and health. Part. B Pesticides food contaminants and agricultural wastes, 2008Co-Authors: Tanya Cáceres, Mallavarapu Megharaj, Ravi NaiduAbstract:The effect of Fenamiphos, a widely used organophosphorus pesticide, on important soil microbial activities such as dehydrogenase, urease and potential nitrification in four soils from Australia and Ecuador were studied. The results showed Fenamiphos in general was not toxic to dehydrogenase and urease up to 100 mg/Kg soil. However potential nitrification was found to be highly sensitive to Fenamiphos with a significant inhibition recorded even at 10 mg/Kg soil. In general, the nitrification activity in soils was decreased with an increase in Fenamiphos concentration. The calculated EC50 values for nitrification in all the tested soils ranged between 19 and 56 mg Fenamiphos/kg dry soil. This study suggests that Fenamiphos is likely to be detrimental to nitrification at field application rates.
-
Biodegradation of the Pesticide Fenamiphos by Ten Different Species of Green Algae and Cyanobacteria
Current microbiology, 2008Co-Authors: Tanya Cáceres, Mallavarapu Megharaj, Ravi NaiduAbstract:The degradation of an organophosphorus pesticide, Fenamiphos, by different species of five green algae and five cyanobacteria was studied. All the species tested were able to transform Fenamiphos to its primary oxidation product, Fenamiphos sulfoxide (FSO), while the majority of these cultures were able to hydrolyze FSO to Fenamiphos sulfoxide phenol (FSOP). Fenamiphos sulfone phenol, FSOP, and FSO were detected in the culture extracts of these algae and cyanobacteria. This is the first report on the biodegradation of a toxic pesticide, Fenamiphos, by cyanobacteria. The ability of these algae and cyanobacteria to detoxify Fenamiphos can be gainfully used in bioremediation of this pesticide and its toxic metabolites.
A. W. Johnson - One of the best experts on this subject based on the ideXlab platform.
-
Fenamiphos LOSSES UNDER SIMULATED RAINFALL: PLOT SIZE EFFECTS
Transactions of the ASAE, 2004Co-Authors: R. D. Wauchope, A. W. Johnson, Clint C. Truman, H. R. Sumner, James E. Hook, C. C. Dowler, L. D. Chandler, G. J. Gascho, Jessica G. DavisAbstract:The purpose of this study was to compare two commonly used runoff experimental methods, which have different scales, on measurements of runoff and associated Fenamiphos and metabolite losses over a 2-year period. Methods used were 15 m wide by 43 m long (645 m2) mesoplots and 1.8 m wide by 3 m long (5.4 m2) microplots, under simulated rainfall (25 mm h-1 for 2 h) at 1, 14, and 28 d after Fenamiphos application. Mesoplots and microplots were established parallel to a 3% slope on a Tifton loamy sand (Plinthic Kandiudult). All plots were planted to corn (Zea mays L.). Target application rate for Fenamiphos was 6.7 kg ha-1. Runoff totals and maximum rates for meso- and microplots were similar, with approximately 25% of the rainfall running off mesoplots and approximately 28% running off microplots. Runoff totals and maximum rates from meso- and microplots were each positively correlated (R2 = 0.89). In both years, Fenamiphos lost in runoff decreased with each rainfall event (1, 14, and 28 d after application). The majority of Fenamiphos lost in runoff was in the Fenamiphos sulfoxide form. Fenamiphos sulfoxide lost over both years from mesoplots ranged from 51% to 93% of the total Fenamiphos lost, and loss from microplots ranged from 47% to 100% of the total Fenamiphos lost. Runoff from meso- and microplots 1 d after Fenamiphos application, a “reasonable worst-case” event, had the greatest Fenamiphos losses among events. Total losses of Fenamiphos for this event averaged 1.2% (CV = 26%) of applied amount for mesoplots and 1.3% (CV = 47%) of applied amount for microplots. Maximum (seasonal) Fenamiphos losses for meso- and microplots were 1.4% of applied for mesoplots and 2.6% of applied for microplots. A positive correlation was obtained between microplots and mesoplots for total losses of Fenamiphos + metabolites (R2 = 0.88), Fenamiphos parent (R2 = 0.89), and Fenamiphos sulfoxide (R2 = 0.81). Relatively poor agreement was found for relatively small losses of Fenamiphos sulfone between plot types (R2 = 0.34). Microplots and mesoplots yielded statistically similar results in terms of runoff and Fenamiphos losses; thus, microplot results can be extrapolated up to larger mesoplot areas under these conditions. This has implications for field-scale management and watershed assessment in the Coastal Plain region of the southeast U.S. in that microplot and rainfall simulation results could be useful as statistically valid input datasets to estimate runoff and associated Fenamiphos losses from larger areas.
-
Effects of a Resistant Corn Hybrid and Fenamiphos on Meloidogyne incognita in a Corn-Squash Rotation.
Journal of nematology, 1999Co-Authors: A. W. Johnson, D. R. Sumner, G. L. Windham, W. P. WilliamsAbstract:The efficacy of a double-cross corn (Zea mays) hybrid (Old Raccoon selection X T216) X (Tebeau selection X Mp 307) resistant to Meloidogyne incognita as a rotational crop, and Fenamiphos treatment for management of root-knot nematode (M. incognita race 1) in squash (Cucurbita pepo var. melopepo) was evaluated in field tests during 1996 and 1997. Numbers of M. incognita in the soil and root-gall indices were lower on the resistant hybrid than on a commercial cultivar DeKalb DK-683. Treatment means across both corn entries had lower root-gall indices following Fenamiphos treatment. In soil collected 2 September 1997, there were more colony-forming units (cfu) per gram of oven-dried soil of Pythium spp. from plots planted to DK-683 treated with Fenamiphos than in untreated plots (88 vs. 59 cfu). Some corn plots had individual plants with 10% to 15% of the crown and brace roots decayed, but no differences due to Fenamiphos treatment. Lodging of stalks was 40% to 50% more in the double-cross hybrid than in DK-683. Yield was greater from DK-683 than the double-cross hybrid. Based on cultivar means across Fenamiphos treatments and Fenamiphos treatment means across cultivars, root-gall indices and yield of squash were significantly lower following the double cross hybrid than DK-683 and in Fenamiphos-treated plots than in untreated plots of squash. Yield of squash was not affected by at-planting treatment with Fenamiphos on the preceding crops of corn. Nematode resistance must be transferred into the elite materials of commercial seed companies to reach its full potential as a nematode management strategy.
-
Fenamiphos transport, transformation, and degradation in a highly weathered soil
Transactions of the ASAE, 1998Co-Authors: C. C. Truman, R.a. Leonard, A. W. JohnsonAbstract:Fenamiphos, a nematicide used on corn and sorghum, quickly oxidizes into two metabolites which have similar activities and toxicities, yet are more mobile and persistent than the parent compound. Given the soil and climatic conditions of the southeastern U.S., Fenamiphos and its metabolites could be transported from the application site and contaminate off-site water bodies. A three-year study was conducted to evaluate (1) degradation and transport of the Fenamiphos parent (Fp) and its metabolites (sulfoxide, Fx, and sulfone, Fo) from a 0.34 ha field site, and (2) the utility of the GLEAMS (Groundwater Loading Effects of Agricultural Management Systems) model in describing system response and simulating pesticide transport. Each year, Fenamiphos was applied at 6.7 kg ha–1 a.i., broadcast and incorporated into the upper 100 mm soil layer before planting each crop. Concentrations of Fenamiphos and its metabolites were determined from soil samples taken within the root zone at 50 mm intervals to a depth of 300 mm and from subsurface tile outflow at selected times throughout each sweet corn (Zea mays L.) and hybrid pearl millet (Pennisetum glaucum (L.) R. Br.) growing season. The GLEAMS model was used to simulate runoff, lateral subsurface flow (LSF), and Fp, Fx, and Fo losses from the Cowarts loamy sand. An average of 6 and 21% of the total rainfall + irrigation was measured as runoff and LSF, respectively. GLEAMS model simulations were correlated with measured runoff (R2 = 0.81) and LSF (R2 = 0.89). Field half-lives (t1/2) were determined by comparing observed concentrations in soil by depth and time to those simulated with the GLEAMS model. Average t1/2 values from measured field data were 5, 28, and 14 days for Fp, Fx, and Fo, respectively. For the three-year study, about 6.2% of the total amount of applied Fenamiphos (Ftot = Fp + Fx + Fo) was measured in LSF, while less than 0.1% of the applied Fenamiphos was measured in surface runoff. Fx was the dominant compound measured and simulated in the root zone and LSF, with 70 to 99% of measured Ftot being Fx. Calibration of the GLEAMS model provided fit of the field data that indicated (1) Fp dissipated rapidly while the two metabolites (Fx and Fo) formed (average Fp t1/2 = 5.5 d); (2) t1/2 values for all compounds remained relatively constant during 1987 and 1988, then numerically decreased in 1989; (3) coefficient of transformation (CT) values for Fx and Fo decreased from 1987 to 1989; and (4) CT values describing transformational changes from Fp to Fx were greater than those describing transformational changes from Fx to Fo. Decreases in t1/2 and CT values for Fp, Fx, and Fo with continued use over the three-year study is characteristic of enhanced microbial degradation.
-
Effect of simulated rainfall on efficacy and leaching of two formulations of Fenamiphos.
Journal of nematology, 1996Co-Authors: A. W. Johnson, R. D. Wauchope, D. R. SumnerAbstract:Recoverable Fenamiphos in the soil and residue in squash following different simulated rainfall treatments after nematicide application were determined in a 2-year study. Efficacy of Fenamiphos also was evaluated. Fenamiphos treatments (3 SC and 15 G) were broadcast (6.7 kg a.i./ha) over plots and incorporated into the top 15 cm of soil immediately before planting 'Dixie Hybrid' squash. Simulated rainfall treatments of 0, 2.5, and 5.0 cm water were applied 1 day after Fenamiphos application. Soil samples from 0- to 8-cm, 8- to 15-cm, and 15- to 30-cm soil depths were collected 1 day after the simulated rainfall applications and analyzed for Fenamiphos, Fenamiphos sulfoxide (FSO), and Fenamiphos sulfone (FSO[sub2]). Squash was analyzed for total Fenamiphos residue. Greater concentrations of Fenamiphos were present in the 0- to 8-cm soil layer following application of 15 G than 3 SC formulation. Simulated rainfall treatments did not alter Fenamiphos concentrations in any soil layer (except for the 0- to 8-cm depth in 1992) or concentration of FSO and total Fenamiphos residue in the 15- to 30-cm soil layer. Root-gall indices were greater from untreated than most Fenamiphos-treated plots, but were not affected by formulations of Fenamiphos or simulated rainfall treatments. Concentrations of total residue in squash ranged from 1 to 4 [mu]g FSO[sub2]/g. Key words: Cucurbita melopepo, efficacy, Fenamiphos, leaching, management, Meloidogyne incognita, nematicide, nematode, root-knot, root-knot nematode, squash.
-
Effect of simulated rainfall on leaching and efficacy of Fenamiphos.
Journal of nematology, 1995Co-Authors: A. W. Johnson, R. D. Wauchope, B. BurgoaAbstract:There is increasing concern in the United States about the pesticide movement in soil, groundwater contamination, and pesticide residue in food. The objective of this study was to determine the efficacy, degradation, and movement of Fenamiphos (Nemacur 15G) in the soil and residues in squash fruit as influenced by four simulated rainfall treatments (2.5 or 5.0 cm each applied 1 or 3 days after nematicide application) under field conditions. In 1990, concentrations of Fenamiphos were greater in the top 15 cm of soil in plots with no rainfall than in those treated with rainfall. Eighty to 95 % of the Fenamiphos recovered from treated plots was found in the 0-15-cm soil layer. The concentration of Fenamiphos recovered from the 0-15-cm soil layer in 1991 was approximately one-half the concentration recovered in 1990, but greater concentrations of Fenamiphos sulfoxide (an oxidation product of Fenamiphos) were recovered in 1991 than in 1990. Concentrations of Fenamiphos, Fenamiphos sulfoxide, and Fenamiphos sulfone were near or below detectable levels (0.002 mg/kg soil) below the 0-15-cm soil layer. Rainfall treatments did not affect the efficacy of the nematicide against Meloidogyne incognita race 1. The concentration of Fenamiphos in squash fruit in 1991 was below the detectable level (0.01 mg/kg).
Denis J. Wright - One of the best experts on this subject based on the ideXlab platform.
-
bioremedial potential of Fenamiphos and chlorpyrifos degrading isolates influence of different environmental conditions
Soil Biology & Biochemistry, 2006Co-Authors: Brajesh K. Singh, Allan Walker, Denis J. WrightAbstract:Previously isolated bacterial strains for chlorpyrifos and Fenamiphos degradation were used to examine their potential as bioremedial agents in soils and water containing pesticide residues. Both, chlorpyrifos-degrading Enterobacter sp and Fenamiphos-degrading consortium rapidly degraded pesticides when inoculated into natural and sterile water and soils. Degradation rate was slower in lower pH soils in comparison with natural and alkaline soils. Soil organic matter had no impact on pesticide degrading ability of isolates. Soil moisture <40% of maximum water-holding capacity slowed down degradation rate. The bacterial isolates were able to rapidly degrade Fenamiphos and chlorpyrifos between 15 and 35 °C but their degradation ability was sharply reduced at 5 and 50 °C. Both groups of bacterial systems were also able to remove a range of pesticide degradation. An inoculum density of 104 cells g−1 of soil was required for initiating rapid growth and degradation. Ageing of pesticide in soils prior to inoculation produced contrasting results. Ageing of Fenamiphos had no impact on subsequent degradation by the inoculated consortium. However, degradation of chlorpyrifos by Enterobacter sp after aging resulted in persistence of ∼10% of pesticide in soil matrix. Higher Koc value of chlorpyrifos may have resulted in a lack of bioavailability of a smaller percentage of chlorpyrifos to degrading bacteria. Overall, this paper confirms bioremedial potential of a Fenamiphos degrading consortium and a chlorpyrifos degrading bacterium under different soil and water characteristics.
-
Bioremedial potential of Fenamiphos and chlorpyrifos degrading isolates: Influence of different environmental conditions
Soil Biology and Biochemistry, 2006Co-Authors: Brajesh K. Singh, Allan Walker, Denis J. WrightAbstract:Previously isolated bacterial strains for chlorpyrifos and Fenamiphos degradation were used to examine their potential as bioremedial agents in soils and water containing pesticide residues. Both, chlorpyrifos-degrading Enterobacter sp and Fenamiphos-degrading consortium rapidly degraded pesticides when inoculated into natural and sterile water and soils. Degradation rate was slower in lower pH soils in comparison with natural and alkaline soils. Soil organic matter had no impact on pesticide degrading ability of isolates. Soil moisture
-
Role of soil pH in the development of enhanced biodegradation of Fenamiphos.
Applied and environmental microbiology, 2003Co-Authors: Brajesh K. Singh, Allan Walker, J. Alun W. Morgan, Denis J. WrightAbstract:Repeated treatment with Fenamiphos (ethyl 4-methylthio-m-tolyl isopropylphosphoramidate) resulted in enhanced biodegradation of this nematicide in two United Kingdom soils with a high pH (≥7.7). In contrast, degradation of Fenamiphos was slow in three acidic United Kingdom soils (pH 4.7 to 6.7), and repeated treatments did not result in enhanced biodegradation. Rapid degradation of Fenamiphos was observed in two Australian soils (pH 6.7 to 6.8) in which it was no longer biologically active against plant nematodes. Enhanced degrading capability was readily transferred from Australian soil to United Kingdom soils, but only those with a high pH were able to maintain this capability for extended periods of time. This result was confirmed by fingerprinting bacterial communities by 16S rRNA gene profiling of extracted DNA. Only United Kingdom soils with a high pH retained bacterial DNA bands originating from the Fenamiphos-degrading Australian soil. A degrading consortium was enriched from the Australian soil that utilized Fenamiphos as a sole source of carbon. The 16S rRNA banding pattern (determined by denaturing gradient gel electrophoresis) from the isolated consortium migrated to the same position as the bands from the Australian soil and those from the enhanced United Kingdom soils in which the Australian soil had been added. When the bands from the consortium and the soil were sequenced and compared they showed between 97 and 100% sequence identity, confirming that these groups of bacteria were involved in degrading Fenamiphos in the soils. The sequences obtained showed similarity to those from the genera Pseudomonas, Flavobacterium, and Caulobacter. In the Australian soils, two different degradative pathways operated simultaneously: Fenamiphos was converted to Fenamiphos sulfoxide (FSO), which was hydrolyzed to the corresponding phenol (FSO-OH) or was hydrolyzed directly to Fenamiphos phenol. In the United Kingdom soils in which enhanced degradation had been induced, Fenamiphos was oxidized to FSO and then hydrolyzed to FSO-OH, but direct conversion to Fenamiphos phenol did not occur.
-
Degradation of chlorpyrifos, Fenamiphos, and chlorothalonil alone and in combination and their effects on soil microbial activity.
Environmental toxicology and chemistry, 2002Co-Authors: Brajesh K. Singh, Allan Walker, Denis J. WrightAbstract:The effects of repeated application and of combinations of pesticides on their degradation rates in soil and on some soil microbial properties were studied. Repeated application of chlorpyrifos did not modify its degradation rate, whereas repeated applications of Fenamiphos and chlorothalonil suppressed their own rates of degradation. When applied in combination, the presence of chlorothalonil reduced the degradation rate of both chlorpyrifos and Fenamiphos, and the half-life of chlorothalonil was extended in the presence of chlorpyrifos. The dynamics of residues of the major metabolites of the different compounds were also affected by the pesticide combinations and, particularly, by the presence of chlorothalonil. The measured soil microbial parameters (enzyme activities and total microbial biomass) were stable in the pesticide-free control soils throughout the 90-d incubation period, but they were all adversely affected by the presence of chlorothalonil in the soil. The effects from Fenamiphos or chlorpyrifos on the soil microbial characteristics were either very small or insignificant.