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Pesticide use in rice farming and its impacts on climbing perch (Anabas testudineus) in the Mekong Delta of Vietnam
Stockholm University, Faculty of Science, Department of Physical Geography. Faculty of Fishery, Nong Lam University, Vietnam. (Environmental, Resource dynamics and Management)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The intensification of agricultural production in the Mekong Delta has faced serious challenges with respect to increased use of agrochemicals and especially pesticides. The indiscriminate use of pesticide could potentially impact on the long-term food production, environmental and human health in the delta. The aim of this thesis was to investigate the negative side effects of the current use of pesticides on climbing perch (Anabas testudineus) in rice fields using brain acetylcholinesterase (hereafter referred to as AChE) activity as a biomarker. The empirical work, on which this thesis is based, includes structured questionnaires, laboratory and field experiments. First, a field survey using questionnaires was carried out to gain a better understanding of the current state of rice farming systems, the use of pesticides and attitude to pest management strategies among rice and rice-fish farmers, as well as to provide basic information for the set-up of the laboratory and field experiments. Secondly, laboratory studies were conducted to clarify if the selected insecticides applied alone and in mixtures caused negative side effects on climbing perch fingerlings. Thirdly, further toxicity studies were carried out, under rice field conditions, to further investigate the toxicity effects of the insecticides, applied alone, in mixtures and under sequential applications, on climbing perch fingerlings.

The results showed that although there were a more selective use of pesticides and an increased awareness among farmers of the negative side effects of pesticides in 2007 as compared to 1999, the current use of pesticide in the Mekong Delta still cause many problems to the environment and human health. Chlorpyrifos ethyl (hereafter referred to as CPF) was found to cause a significant and more prolonged inhibition on the brain AChE activity in climbing perch than fenobucarb (hereafter referred to as F). The inhibition by the mixture of CPF and F were significantly higher than the inhibition by only F, but less prolonged and significant lower than the inhibition by only CPF. The results suggest that the combined effect from a mixture of F and CPF can create both additive effects initially and later antagonistic effects.

CPF and F applied at concentrations used by farmers, either as separate doses, in a mixture or in sequential doses, decreased the brain AChE activity, growth and survival rates in climbing perch. The results demonstrate that brain AChE activity in climbing perch is a relevant biomarker for monitoring of exposure to, and sub-lethal impacts from organophosphates and carbamates under tropical conditions. The result also shows that 2-PAM re-activate the brain AChE activity, and can be used as an alternative method to assess the AChE inhibition level in organisms recently exposed to OP’s, in situation where it may be difficult to find unexposed individuals as controls.

In conclusion, this thesis shows that the current use of pesticides in the Mekong Delta has a negative effect on climbing perch living in rice fields. It indicates that a sustained long-term food production in the Mekong Delta must be based on ecological principles, taking advantages of ecosystem biodiversity and productivity, and not through intensified use of pesticides.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography, Stockholm University , 2016. , 42 p.
Series
Dissertations from the Department of Physical Geography, ISSN 1653-7211 ; 55
Keyword [en]
Mekong Delta, Rice field, Climbing perch, Insecticide, Chlorpyrifos ethyl, Fenobucarb, Mixture, Sequential applications, AChE
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
URN: urn:nbn:se:su:diva-128856ISBN: 978-91-7649-415-8 (print)OAI: oai:DiVA.org:su-128856DiVA: diva2:917234
Public defence
2016-05-27, William Olsson-salen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 5: Submitted.

Available from: 2016-05-02 Created: 2016-04-05 Last updated: 2017-02-23Bibliographically approved
List of papers
1. Use of pesticides and attitude to pest management strategies among rice and rice-fish farmers in the Mekong Delta, Vietnam
Open this publication in new window or tab >>Use of pesticides and attitude to pest management strategies among rice and rice-fish farmers in the Mekong Delta, Vietnam
2012 (English)In: International Journal of Pest Management, ISSN 0967-0874, E-ISSN 1366-5863, Vol. 58, no 2, 153-164 p.Article in journal (Refereed) Published
Abstract [en]

This study assesses the use of pesticides and attitude to pest management strategies among rice and rice-fish farmersin Can Tho’ and Tien Giang provinces of the Mekong Delta, Vietnam, in 2007. A comparison is made to a similarstudy in 1999, in order to identify changes in patterns of pesticide use and possible influences of integrated pestmanagement (IPM) programmes and brown planthopper (a major pest) outbreaks. One hundred and twenty farmersused 66 different pesticides, similar to the 64 pesticides recorded as being used in the 1999 survey. Nine of the 10 mostpopular pesticides in 2007 were the same as those found to be popular in 1999. Insecticides are used by 73–95% ofthe farmers, which is the most commonly employed type of pesticide. The number of applications of both herbicidesand fungicides has more than halved since 1999 for all farmers, while insecticide applications has doubled for IPMfarmers (those with prior training in IPM methodology). Similarly, the average dose of active ingredient (a.i.) ofinsecticides per crop has decreased slightly for non-IPM rice farmers, while it has more than doubled among IPMfarmers, resulting in almost the same amount of a.i. per crop for all groups of farmers (insecticides 0.6, fungicides 0.5,and herbicides 0.3 kg a.i. ha71 crop71). Overall, the results indicate a temporal trend for more selective use ofpesticides and an increased awareness among non-IPM farmers of the negative side effects of pesticide use.

Keyword
agro-ecosystem, IPM, Mekong Delta, pesticides, rice-fish farming
National Category
Agricultural Sciences Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-128412 (URN)10.1080/09670874.2012.672776 (DOI)000304833400008 ()
Available from: 2016-03-27 Created: 2016-03-27 Last updated: 2017-11-30Bibliographically approved
2. Effect of Chlorpyrifos Ethyl on Acetylcholinesterase Activityin Climbing Perch (Anabas testudineus, Bloch, 1972)
Open this publication in new window or tab >>Effect of Chlorpyrifos Ethyl on Acetylcholinesterase Activityin Climbing Perch (Anabas testudineus, Bloch, 1972)
2015 (English)In: Archives of Environmental Contamination and Toxicology, ISSN 0090-4341, E-ISSN 1432-0703, Vol. 69, no 4, 515-524 p.Article in journal (Refereed) Published
Abstract [en]

The high use of pesticides in intensive rice farming in the Mekong Delta constitutes a potential hazard to the environment and to people's health. Chlorpyrifos ethyl (CPF) is a commonly used organophosphate (OP) insecticide, but information about its potential negative impacts on the aquatic environment in the Mekong Delta is scarce. Both acute and subacute toxicity tests were performed in a static nonrenewable system to investigate the effects of CPF on brain acetylcholinesterase (AChE) activity in native climbing perch fingerlings (Anabas testudineus, Bloch, 1972). Environmental parameters, such as dissolved oxygen, water temperature, and pH, were similar to field conditions in the Mekong Delta. In a 96-h lethal concentration (LC50) test, fingerlings of climbing perch were randomly exposed to five levels of CPF ranging from 0.8 to 4.5 ppm. Five sublethal levels of CPF (1, 5, 10, 15, and 20 % of the 96-h LC50 value) were tested to assess the sensitivity and recovery of the brain AChE activity in climbing perch fingerlings exposed to CPF. The results showed that CPF were moderately toxic to climbing perch with a 96-h median LC50 of 1.73 ppm. CPF also caused long-term AChE inhibition with 70 % inhibition remaining after 96 h for the four highest test concentrations. The recovery of brain AChE activity in fish placed in CPF-free water was very slow, and after 7 days the brain AChE activity was still significant lower in fish from the four highest concentrations compared with the control. The results from this study indicate that OP insecticides, such as CPF, can have long-lasting sublethal effects on aquatic species in the Mekong Delta.

National Category
Agricultural Sciences Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-122158 (URN)10.1007/s00244-015-0182-3 (DOI)000362666700014 ()
Available from: 2015-10-27 Created: 2015-10-27 Last updated: 2017-12-01Bibliographically approved
3. The joint effect of chlorpyrifos ethyl and fenobucarb on brain acetylcholinesterase activity in climbing perch (Anabas testudineus) fingerlings
Open this publication in new window or tab >>The joint effect of chlorpyrifos ethyl and fenobucarb on brain acetylcholinesterase activity in climbing perch (Anabas testudineus) fingerlings
(English)Manuscript (preprint) (Other academic)
National Category
Agricultural Sciences Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-122163 (URN)
Available from: 2015-10-27 Created: 2015-10-27 Last updated: 2016-06-10Bibliographically approved
4. Effects of chlorpyrifos ethyl on acetylcholinesterase activity in climbing perch cultured in rice fields in the Mekong Delta, Vietnam
Open this publication in new window or tab >>Effects of chlorpyrifos ethyl on acetylcholinesterase activity in climbing perch cultured in rice fields in the Mekong Delta, Vietnam
2015 (English)In: Ecotoxicology and Environmental Safety, ISSN 0147-6513, E-ISSN 1090-2414, Vol. 117, 34-40 p.Article in journal (Refereed) Published
Abstract [en]

Climbing perch is commonly harvested in rice fields and associated wetlands in the Mekong Delta. Despite its importance in providing food and income to local households, there is little information how this fish species is affected by the high use of pesticides in rice farming. Organophosphate insecticides, such as chlorpyrifos ethyl, which are highly toxic to aquatic organisms, are commonly used in the Mekong Delta. This study shows that the brain acetylcholinesterase (AChE) activity in climbing perch fingerlings cultured in rice fields, was significantly inhibited by a single application of chlorpyrifos ethyl, at doses commonly applied by rice farmers (032-0.64 kg/ha). The water concentration of chlorpyrifos ethyl decreased below the detection level within 3 days, but the inhibition of brain AChE activity remained for more than 12 days. In addition, the chlorpyrifos ethyl treatments had a significant impact on the survival and growth rates of climbing perch fingerlings, which were proportional to the exposure levels. The results indicate that the high use of pesticides among rice farmers in the Mekong Delta could have a negative impact on aquatic organisms and fish yields, with implications for the aquatic biodiversity, local people's livelihoods and the aquaculture industry in the Mekong Delta.

Keyword
Climbing perch, Chlorpyrifos ethyl, Acetylcholinesterase, Mekong Delta, Pesticides, Rice farming
National Category
Earth and Related Environmental Sciences Agricultural Science
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-118332 (URN)10.1016/j.ecoenv.2015.03.020 (DOI)000354501500005 ()
Available from: 2015-07-21 Created: 2015-06-15 Last updated: 2017-12-04Bibliographically approved
5. The joint toxicity effects of Chlorpyrifos ethyl and Fenobucarb to Climbing perch (Anabas testudineus) from rice fields in the Mekong Delta, Vietnam
Open this publication in new window or tab >>The joint toxicity effects of Chlorpyrifos ethyl and Fenobucarb to Climbing perch (Anabas testudineus) from rice fields in the Mekong Delta, Vietnam
2016 (English)In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499Article in journal (Refereed) Epub ahead of print
Abstract [en]

Organophosphates (e.g. chlorpyrifos ethyl) and carbamates (e.g. fenobucarb), are commonly used to control a wide range of pests in rice fields of the Mekong Delta in Vietnam. This study assesses the combined effect of chlorpyrifos ethyl (CPF) and fenobucarb (F) on the brain acetylcholinesterase (AChE) activity in climbing perch fingerlings from rice fields in the Mekong Delta. It also investigates if Pyridine-2-aldoxime methiodide (2-PAM) can be used to re-activate cholinesterase that has been blocked by CPF and F. Three days after spraying, the water concentrations of both insecticides decreased quickly below the detection levels. However the brain AChE activity in fish was inhibited for more than seven days. The results indicate a quicker but less prolonged inhibition of the brain AChE activity by the mixture than by only CPF. The inhibition levels were above 70% only during the first 48 hours, which could explain why all fish survived. 2-PAM resulted in a significant re-activation of the cholinesterase blocked by a combination of CPF and F, and it is proposed that the re-activation by 2-PAM could provide a way to assess the AChE inhibition level in organisms, when no unexposed individuals are available as controls. The results indicate that current use of CPF and F in rice farming in the Mekong Delta is likely to cause negative effects on non-target organisms. Many of these effects may be sub-lethal, and there is a need to develop relevant bio-markers, that are relevant, cheap and easy to apply under tropical conditions in developing countries.

Keyword
Anabas testudineus, Chlorpyrifos ethyl, Fenobucarb, Mixture, Acetylcholinesterase, Mekong Delta
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-128415 (URN)10.1007/s11356-016-6980-y (DOI)
Projects
Swedish International Development Cooperation Agency (Sida) (Ref. No. AKT2010-010) through the Partner Driven Cooperation (PDC) project “Managing Ecosystem Services for Sustainable Aquaculture Development.
Available from: 2016-03-27 Created: 2016-03-27 Last updated: 2017-12-06
6. Effects of Sequential Applications of Bassa 50EC (Fenobucarb) and Vitashield 40EC (Chlorpyrifos ethyl) on Acetylcholinesterase Activity in Climbing Perch (Anabas testudineus) Cultured in Rice Fields in the Mekong Delta, Vietnam
Open this publication in new window or tab >>Effects of Sequential Applications of Bassa 50EC (Fenobucarb) and Vitashield 40EC (Chlorpyrifos ethyl) on Acetylcholinesterase Activity in Climbing Perch (Anabas testudineus) Cultured in Rice Fields in the Mekong Delta, Vietnam
Show others...
2016 (English)In: Bulletin of Environmental Contamination and Toxicology, ISSN 0007-4861, E-ISSN 1432-0800, Vol. 97, no 1, 98-104 p.Article in journal (Refereed) Published
Abstract [en]

This study assesses the effects of sequential applications of the insecticides Bassa 50EC (fenobucarb-F) and Vitashield 40EC (chlorpyrifos ethyl-CPF), sprayed at concentrations used by rice farmers in the Mekong Delta, on the brain acetylcholinesterase (AChE) in climbing perch fingerlings. After spraying the pesticides on the rice fields, the water concentrations of both insecticides decreased below the detection levels within three days. The sequential applications caused significant inhibition on the brain AChE activity in the exposed fish. The inhibition by F was quicker, but less prolonged, than for CPF. The inhibition levels caused by the sequential applications were lower than those caused by only CPF and by a mixture of CPF and F. The results indicate that sequential applications of pesticides could have a negative impact on aquatic organisms and fish yields, with implication for the aquatic biodiversity, local people’s livelihood and the aquaculture industry in the Mekong Delta.

Keyword
Climbing perch, Chlorpyrifos ethyl, Fenobucarb, Acetylcholinesterase, Mekong Delta
National Category
Earth and Related Environmental Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-128416 (URN)10.1007/s00128-016-1796-5 (DOI)000378779300017 ()
Projects
Swedish International Development Cooperation Agency (Sida) (Ref. no. AKT2010-010) through the Partner Driven Cooperation (PDC) project “Managing Ecosystem Services for Sustainable Aquaculture Development.
Available from: 2016-03-27 Created: 2016-03-27 Last updated: 2017-11-30Bibliographically approved

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