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Barker K. R. - One of the best experts on this subject based on the ideXlab platform.
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Differential Sensitivity of Meloidogyne spp. and Heterodera glycines to Selected Nematicides
Society of Nematologists, 2026Co-Authors: Gourd T. R., Schmitt D. P., Barker K. R.Abstract:Differential sensitivity of Meloidogyne arenaria, M. hapla, M. incognita, M. javanica, and Heterodera glycines races 1 and 5 to the nonfumigant nematicides aldicarb, Ethoprop, and fenamiphos was evaluated using a 48-hour root-penetration bioassay. Generally, H. glycines was more tolerant of the nematicides, especially Ethoprop, than were the Meloidogyne species. Among Meloidogyne species, M. incognita was most sensitive to aldicarb and fenamiphos, but its reaction to Ethoprop was similar to the other three Meloidogyne species
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Population Changes of Heterodera glycines and Soybean Yields Resulting from Soil Treatment with Alachlor, Fenamiphos, and Ethoprop
Society of Nematologists, 2026Co-Authors: Bostian A. L., Schmitt D. P., Barker K. R.Abstract:The population dynamics of Heterodera glycines as influenced by alachlor, fenamiphos, and Ethoprop alone and in herbicide-nematicide combinations were studied in the field. Numbers of H. glycines juveniles and eggs were higher at midseason and harvest where nematicides were applied. Fenamiphos alone or in combination with alachlor provided better control of H. glycines and greater seed yields than treatments with Ethoprop. Numbers of H. glycines eggs at harvest in 1980 were positively correlated with numbers of juveniles at planting in 1981 and negatively related to seed yield in 1981
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Temporal Efficacy of Selected Nematicides on Meloidogyne Species on Tobacco
Society of Nematologists, 2026Co-Authors: Melton T. A., Barker K. R., Koenning S. R., Powell N. T.Abstract:Aldicarb, Ethoprop, and fenamiphos were evaluated for their efficacy in controlling various species of root-knot nematodes on flue-cured tobacco and for their residual activity, as determined through periodic sampling and bioassays of soil taken from field plots. Field experiments were conducted at five locations over 2 years with flue-cured tobacco. Soil in plots treated with nematicides were formed into high, wide beds before transplanting with 'Coker 371-Gold' or 'K 326' tobacco. Residual control of Meloidogyne spp. was greatest (P ≤ 0.05) with fenamiphos (in some cases up to 10 weeks, as measured in tomato bioassays of infested soil and root fragments). Suppression of nematode reproduction by Ethoprop was short-lived, and numbers of second-stage juveniles + eggs and numbers of galls in bioassays sometimes surpassed those of untreated plots within 4 weeks after treatment. Aldicarb gave intermediate control over time as compared to the other compounds. Although nematicidal efficacy of all compounds varied with site and season, fenamiphos and aldicarb generally produced the highest yields
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Interrelationships of Meloidogyne Species with Flue-cured Tobacco
Society of Nematologists, 2026Co-Authors: Barker K. R., Todd F. A., Shane W. W., Nelson L. A.Abstract:Microplot and field experiments were conducted to determine relationships of population densities of Meloidogyne spp. to performance of flue-cured tobacco. A 3-yr microplot study of these interactions involved varying initial nematode numbers (Pi).and use of Ethoprop to re-establish ranges of nematode densities. Field experiments included various nematicides at different locations. Regression analyses of microplot data from a loamy sand showed that cured-leaf yield losses on 'Coker 319' for each 10-fold increase in Pi were as follows: M. javanica and M. arenaria—-13-19%; M. incognita—5-10%; M. hapla—3.4-5%; and 3% for M. incognita on resistant 'Speight G-28' tobacco. A Pi of 750 eggs and larvae/500 cm³ of soil of all species except M. hapla caused a significant yield loss; only large numbers of M. hapla effected a loss. M. arenaria was the most tolerant species to Ethoprop. Root-gall indices for microplot and most field-nematicide tests also were correlated negatively with yield. Relationships of Pi(s) and necrosis indices to yield were best characterized by linear regression models, whereas midseason numbers of eggs plus larvae (Pm) and sometimes gall indices vs. yield were better characterized by quadratic models. The relation of field Pm and yield was also adequately described by the Seinhorst model. Degrees of root galling, root necrosis, yield losses, and basic rates of reproduction on tobacco generally increased from M. hapla to M. incognita to M. arenaria to M. javanica
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Influence of Aldicarb on the Growth and Yield of Tobacco
Society of Nematologists, 2026Co-Authors: Barker K. R., Powell N. T.Abstract:Microplot and field experiments were used to examine the plant-growth stimulation frequently associated with the use of aldicarb on tobacco in the absence of major pests. Aldicarb rates of 1.5-4.5 kg a.i./ha enhanced tobacco growth and yield in most experiments, but higher rates (≥ 4.5 kg) usually resulted in a neutral to negative effect. Tobacco cultivars NC 82 and Speight G-28 were more responsive than McNair 944 to the pesticide in microplots. Supplemental irrigation enhanced the responsiveness of Speight G-70 tobacco and McNair 944 to aldicarb, but excessive moisture (ca. 7-8 cm/week) limited cured-leaf yields. Aldicarb also resulted in the greatest mean tobacco yields in 35 field experiments involving Meloidogyne spp. over 3 years, relative to Ethoprop, 1,3-dichloropropene (1,3-D), 1,3-D + chloropicrin, and nontreated controls. Thus, aldicarb generally enhanced tobacco growth and yield in the presence or absence of nematodes, but its impact is dependent on other variables, including cultivar, soil moisture, and soil type
Nathaniel L Scholz - One of the best experts on this subject based on the ideXlab platform.
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sublethal neurotoxicity of organophosphate insecticides to juvenile coho salmon
Aquatic Toxicology, 2020Co-Authors: Cathy A Laetz, David H Baldwin, Nathaniel L ScholzAbstract:Abstract For decades, organophosphate (OP) insecticides have been used as chemical control agents in watersheds that support at-risk populations of Pacific salmon throughout western North America. Spray drift, runoff, and other processes transport OPs to critical surface water habitats for migratory salmonids. While most OPs share a common mechanism of action (i.e., inhibition of neuronal acetylcholinesterase, or AChE), they typically vary in toxic potency. Moreover, dose-response relationships for exposure and sublethal neurotoxicity (e.g., brain AChE inhibition) in salmonids have not been defined for many OPs. Here we exposed juvenile coho salmon (Oncorhynchus kisutch) to five common anticholinesterase insecticides (dimethoate, Ethoprop, naled, phorate and phosmet) that are widely used on agricultural, commercial, residential, and public lands. Each of the five pesticides produced a concentration-dependent inhibition of AChE enzyme activity. The effective concentration for 50 % AChE inhibition (96-hr EC50) indicated the highest toxicity for phorate (EC50 = 0.57 μg/L) followed by phosmet (3.3 μg/L), naled (7.8 μg/L), Ethoprop (90.6 μg/L) and dimethoate (273 μg/L). These findings can inform 1) relative hazard analyses for OP use near sensitive aquatic habitats, 2) predictions of sublethal OP mixture toxicity, and 3) ecological risk assessments for threatened or endangered species of Pacific salmon.
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interactive neurobehavioral toxicity of diazinon malathion and Ethoprop to juvenile coho salmon
Environmental Science & Technology, 2013Co-Authors: Cathy A Laetz, David H Baldwin, John D. Stark, Vincent R Hebert, Nathaniel L ScholzAbstract:In western North America, mixtures of current use pesticides have been widely detected in streams and other aquatic habitats for threatened and endangered Pacific salmon and steelhead (Oncorhynchus sp.). These include organophosphate insecticides that inhibit acetylcholinesterase (AChE) enzyme activity in the salmon nervous system, thereby disrupting swimming and feeding behaviors. Several organophosphates have been shown to interact as mixtures to produce synergistic AChE inhibition at concentrations near or above the upper range of surface water detections in freshwater systems. To evaluate potential synergism at lower concentrations (near or below 1 part per billion), juvenile coho (Oncorhynchus kisutch) were exposed to a range of mixtures of diazinon-malathion and Ethoprop-malathion below a cumulative 0.05 of the predicted EC50 for AChE inhibition, as determined from single chemical concentration–response curves. Brain enzyme inhibition was concentration-dependent, with a 90% reduction and a significa...
Cathy A Laetz - One of the best experts on this subject based on the ideXlab platform.
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sublethal neurotoxicity of organophosphate insecticides to juvenile coho salmon
Aquatic Toxicology, 2020Co-Authors: Cathy A Laetz, David H Baldwin, Nathaniel L ScholzAbstract:Abstract For decades, organophosphate (OP) insecticides have been used as chemical control agents in watersheds that support at-risk populations of Pacific salmon throughout western North America. Spray drift, runoff, and other processes transport OPs to critical surface water habitats for migratory salmonids. While most OPs share a common mechanism of action (i.e., inhibition of neuronal acetylcholinesterase, or AChE), they typically vary in toxic potency. Moreover, dose-response relationships for exposure and sublethal neurotoxicity (e.g., brain AChE inhibition) in salmonids have not been defined for many OPs. Here we exposed juvenile coho salmon (Oncorhynchus kisutch) to five common anticholinesterase insecticides (dimethoate, Ethoprop, naled, phorate and phosmet) that are widely used on agricultural, commercial, residential, and public lands. Each of the five pesticides produced a concentration-dependent inhibition of AChE enzyme activity. The effective concentration for 50 % AChE inhibition (96-hr EC50) indicated the highest toxicity for phorate (EC50 = 0.57 μg/L) followed by phosmet (3.3 μg/L), naled (7.8 μg/L), Ethoprop (90.6 μg/L) and dimethoate (273 μg/L). These findings can inform 1) relative hazard analyses for OP use near sensitive aquatic habitats, 2) predictions of sublethal OP mixture toxicity, and 3) ecological risk assessments for threatened or endangered species of Pacific salmon.
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interactive neurobehavioral toxicity of diazinon malathion and Ethoprop to juvenile coho salmon
Environmental Science & Technology, 2013Co-Authors: Cathy A Laetz, David H Baldwin, John D. Stark, Vincent R Hebert, Nathaniel L ScholzAbstract:In western North America, mixtures of current use pesticides have been widely detected in streams and other aquatic habitats for threatened and endangered Pacific salmon and steelhead (Oncorhynchus sp.). These include organophosphate insecticides that inhibit acetylcholinesterase (AChE) enzyme activity in the salmon nervous system, thereby disrupting swimming and feeding behaviors. Several organophosphates have been shown to interact as mixtures to produce synergistic AChE inhibition at concentrations near or above the upper range of surface water detections in freshwater systems. To evaluate potential synergism at lower concentrations (near or below 1 part per billion), juvenile coho (Oncorhynchus kisutch) were exposed to a range of mixtures of diazinon-malathion and Ethoprop-malathion below a cumulative 0.05 of the predicted EC50 for AChE inhibition, as determined from single chemical concentration–response curves. Brain enzyme inhibition was concentration-dependent, with a 90% reduction and a significa...
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Interactive Neurobehavioral Toxicity of Diazinon, Malathion, and Ethoprop to Juvenile Coho Salmon
2013Co-Authors: Cathy A Laetz, David H. Baldwin, Vincent Hebert, John D. Stark, Nathaniel L. ScholzAbstract:In western North America, mixtures of current use pesticides have been widely detected in streams and other aquatic habitats for threatened and endangered Pacific salmon and steelhead (Oncorhynchus sp.). These include organophosphate insecticides that inhibit acetylcholinesterase (AChE) enzyme activity in the salmon nervous system, thereby disrupting swimming and feeding behaviors. Several organophosphates have been shown to interact as mixtures to produce synergistic AChE inhibition at concentrations near or above the upper range of surface water detections in freshwater systems. To evaluate potential synergism at lower concentrations (near or below 1 part per billion), juvenile coho (Oncorhynchus kisutch) were exposed to a range of mixtures of diazinon-malathion and Ethoprop-malathion below a cumulative 0.05 of the predicted EC50 for AChE inhibition, as determined from single chemical concentration–response curves. Brain enzyme inhibition was concentration-dependent, with a 90% reduction and a significant decrease in spontaneous swimming speed at the highest binary mixture concentrations evaluated (diazinon-malathion at 2.6 and 1.1 μg/L, respectively; Ethoprop-malathion at 2.8 and 1.2 μg/L, respectively). Brain enzyme activity gradually recovered over six weeks. Our findings extend earlier observations of organophosphate synergism in salmon and reveal an unusually steep concentration–response relationship across a mere 2-fold increase in mixture concentration
Johnson A. W. - One of the best experts on this subject based on the ideXlab platform.
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Morphological Comparison of Meloidogyne Males by Scanning Electron Microscopy
Society of Nematologists, 2026Co-Authors: Rohde W. A., Johnson A. W., Dowlet C. C., Glaze N. C.Abstract:Field plots of Tifton loamy sand were treated with methyl bromide, DD-MENCS, or Ethoprop for control of root-knot nematodes, Meloidogyne incognita, in a multiple cropping system of turnips, field corn, and southern peas. Annual applications of methyl bromide and DD-MENCS in November or December suppressed nematode numbers to very low levels through September, but numbers increased in the following October, November, and/or December. No benefit was found from Ethoprop applied to DD-MENCS-treated plots before the planting of each crop. Nematode numbers were not significantly suppressed by Ethoprop alone. Concentrations of Ethoprop in the 0-15-cm soil layer were near 6 μg/g at application but were < 1μg/g of soil 5 days later on corn and southern peas and 30 days later on turnips. Ethoprop concentrations of 4.6 to 5.6 μg/g of soil are too low for adequate control of root-knot nematodes on field corn and southern peas in multiple cropping systems. Stepwise regression analyses indicated that 81% and 36% of the variations in concentration of Ethoprop in the soil were attributable to the amount of water that the plots received when the maximum soil temperature ranged from 10 C to 19 C and from 31 C to 41 C, respectively, and that 11% was attributable to the maximum soil temperature within the temperature range of 17 C to 33 C
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Effects of Film Mulch and Soil Pesticides on Nematodes, Weeds, and Yields of Vegetable Crops
Society of Nematologists, 2026Co-Authors: Johnson A. W., Glaze N. C., Jaworski C. A., Sumner D. R., Chalfant R. B.Abstract:Field plots in Tifton loamy sand were treated with various soil pesticides in 1973 and 1974 and either left exposed or covered with biodegradable flint mulch. Test crops were cantaloup, slicing and pickling cucumber, squash, and sweet corn. Overhead sprinkler irrigation was used in 1973, and trickle irrigation under the film mulch was used on sweet corn in 1974. Soil was assayed for nematodes, and roots of plants were evaluated for damage by root-knot nematodes. Nematode populations were reduced by soil treatment with an organic phosphate or carbamate nematicide-herbicide-fungicide combination (NHF), DD-MENCS, methyl bromide-chloropicrin (MBR-CP), Ethoprop, carbofuran, and sodium azide + Ethoprop or carbofuran. Sodium azide, sodium azide + Ethoprop or carbofuran, Ethoprop, and carbofuran were less effective than DD-MENCS, MBR-CP, attd the NHF combination. The NHF combination controlled grasses and broadteaf weeds as effectively as the herbicide alone. Growth and yield were greatest when nematodes and weeds were controlled. Yields of marketable vegetables were highest from plants in plots treated with DD-MENCS with a film mulch
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Applying Nematicides through an Overhead Sprinkler Irrigation System for Control of Nematodes
Society of Nematologists, 2026Co-Authors: Johnson A. W., Young J. R., Mullinix B. G.Abstract:Phenamiphos, Ethoprop, and carbofuran each at 6.7 kg a.i./ha were applied to squash, southern pea, and corn via injection into a sprinkler irrigation system. This method was then compared with a conventional application of phenamiphos and Ethoprop granules spread on the soil surface and incorporated into the top 15 cm for control of Macroposthonia ornata and Meloidogyne incognita. Nematode populations in the soil and root-gall indices were lower, and yields greater, in treated than in untreated plots, but there were no significant differences between the methods of application in most comparisons
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Analysis of 1,3-Dichloropropene for Control of Meloidogyne spp. in a Tobacco Pest Management System
Society of Nematologists, 2026Co-Authors: Fortnum B. A., Johnson A. W., Lewis S. A.Abstract:1,3-Dichloropropene (1,3-D) and nonfumigant nematicides were evaluated for control of Meloidogyne spp. and soil and foliar insects in a tobacco pest management system. In a field with a high Meloidogyne spp. population density (root gall index 4.0 to 4.5 on a 0 to 10 scale in untreated controls), tobacco yields and crop values increased (482 kg/ha and $1,784/ha for 1, 3-D; 326 kg/ha and $1,206/ha for fenamiphos; 252 kg/ha and $933/ha for Ethoprop) with nematicide application over an untreated control. In fields with a low population density of Meloidogyne arenaria or M. incognita (root gall index 2.3 to 2.5 in untreated controls), yields ranged from 1,714 to 2,027 kg/ha and were not altered by fumigant or nonfumigant nematicide application. Carbofuran, a soil-applied nonfumigant nematicide/insecticide, reduced the number of foliar insecticide applications required to keep insect populations below treatment threshold (3.8 vs. 4.5, respectively, for treated vs. untreated). Carbofuran reduced the cost ($23/ha) of foliar insecticide treatments when compared to an untreated control. Although nonfumigant nematicides provided some soil and foliar insect control, the cost of using a fumigant plus a lower insecticidal rate of a soil insecticide/nematicide was comparable to the least expensive non-fumigant nematicide when the cost of foliar insecticide applications was included in the cost estimates. Savings in foliar insecticide cost by use of soil-applied nonfumigant nematicide/insecticides were small ($23/ha) in comparison to potential value reductions by root-knot nematodes when the nonfumigant nematicides fenamiphos or Ethoprop ($578/ha and $851/ha, respectively) were used instead of 1,3-D
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Effects of Management Practices on Nematode and Fungi Populations and Okra Yield
Society of Nematologists, 2026Co-Authors: Johnson A. W., Jaworski C. A., Sumner D. R., Chalfant R. B.Abstract:Okra was grown in field plots of Tifton loamy sand naturally infested with the nematodes Meloidogyne incognita and Criconemoides ornalus and the pathogenic fungi Fusarium oxysporum, F. solani, F. roseum, and Pythium spp. Plots were treated with various soil pesticides and left exposed or covered with biodegradable paper film mulch under trickle irrigation. Soil was assayed for nematodes and fungi, and plant roots were examined for root-rot and insect damage. Fewer nematodes and fungi generally were recovered from soil treated with DD-MENCS (with and without film mulch) or methyl bromide-chloropicrin (2:1) (MBC) and film mulch than from nontreated soil. Funfigation with DD-MENCS or MBC suppressed populations of M. incognita, C. ornatus, F. oxysporum, F. solani, F. roseum, and Pythium spp. Ethoprop (alone or combined with other pesticides), sodium azide, and chloroneb were less effective than DD-MENCS and MBC. Plant growth anti yield were greatest when nematodes and pathogenic fungi were controlled. Yield was increased 3-fold by DD-MENCS + film mulch or MBC + film mulch in comparison with the average yield of okra produced in Georgia. The root-knot nematode-Fusarium wilt complex was most severe in nonfuntigated soil
Nelson L. A. - One of the best experts on this subject based on the ideXlab platform.
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Population Dynamics of Heterodera glycines and Soybean Response in Soils Treated with Selected Nematicides and Herbicides
Society of Nematologists, 2026Co-Authors: Schmitt D. P., Corbin F. T., Nelson L. A.Abstract:Two field experiments were conducted in two locations to determine the effects of the nematicides aldicarb, phenamiphos, and Ethoprop and/or the herbicides alachlor, linuron, or metribuzin on the population dynamics of Heterodera glycines and soybean growth and yield. Population densities of H. glycines were greater, at some time during the growing season, in several treatments with alachlor alone and in combination with nematicides. Numbers of H. glycines at harvest were greater in plots treated with aldicarb than in those treated with Ethoprop or phenamiphos. The numbers in aldicarb treated plots were generally reduced when plots also received a herbicide. Soybean yields were negatively correlated with numbers of H. glycines eggs and juveniles in early to mid season but positively correlated with late season population densities
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Interrelationships of Meloidogyne Species with Flue-cured Tobacco
Society of Nematologists, 2026Co-Authors: Barker K. R., Todd F. A., Shane W. W., Nelson L. A.Abstract:Microplot and field experiments were conducted to determine relationships of population densities of Meloidogyne spp. to performance of flue-cured tobacco. A 3-yr microplot study of these interactions involved varying initial nematode numbers (Pi).and use of Ethoprop to re-establish ranges of nematode densities. Field experiments included various nematicides at different locations. Regression analyses of microplot data from a loamy sand showed that cured-leaf yield losses on 'Coker 319' for each 10-fold increase in Pi were as follows: M. javanica and M. arenaria—-13-19%; M. incognita—5-10%; M. hapla—3.4-5%; and 3% for M. incognita on resistant 'Speight G-28' tobacco. A Pi of 750 eggs and larvae/500 cm³ of soil of all species except M. hapla caused a significant yield loss; only large numbers of M. hapla effected a loss. M. arenaria was the most tolerant species to Ethoprop. Root-gall indices for microplot and most field-nematicide tests also were correlated negatively with yield. Relationships of Pi(s) and necrosis indices to yield were best characterized by linear regression models, whereas midseason numbers of eggs plus larvae (Pm) and sometimes gall indices vs. yield were better characterized by quadratic models. The relation of field Pm and yield was also adequately described by the Seinhorst model. Degrees of root galling, root necrosis, yield losses, and basic rates of reproduction on tobacco generally increased from M. hapla to M. incognita to M. arenaria to M. javanica