20 K.L. Heong, K.H. Tan, C.P.F. Garcia, L.T. Fabellar, <strong>and</strong> Z. Lu
An <strong>in</strong>secticide is a pesticide used to kill or elim<strong>in</strong>ate <strong>in</strong>sect pests <strong>in</strong> agriculture, households, <strong>and</strong> <strong>in</strong>dustries. Judicious use of <strong>in</strong>secticides may be a factor <strong>in</strong> the <strong>in</strong>crease of agricultural productivity. But, by their nature of hav<strong>in</strong>g high toxicity to nontarget organisms <strong>and</strong> capability to develop resistance through widespread use, most <strong>in</strong>secticides have high potential to signifi cantly affect <strong>and</strong> alter ecosystems. Many are toxic to humans <strong>and</strong> animals (both domestic <strong>and</strong> wildlife), <strong>and</strong> can accumulate as concentrates <strong>in</strong> the food cha<strong>in</strong> <strong>and</strong> water resources, giv<strong>in</strong>g rise to serious environmental contam<strong>in</strong>ation <strong>and</strong> pollution. Toxicity of a chemical is usually expressed <strong>in</strong> relative toxicity. All chemicals, even those generally considered nontoxic, can become toxic depend<strong>in</strong>g on the dosage given to an organism. As such, even a common consumable substance such as water has an LD 50 of just over 80 g/kg, sugar (sucrose) an LD 50 of 30 g/kg, <strong>and</strong> alcohol (ethanol) an LD 50 of 13.7 g/kg, <strong>and</strong> these can be toxic above a certa<strong>in</strong> dosage. Therefore, most <strong>in</strong>secticides, like other toxic chemicals, have vary<strong>in</strong>g degrees of toxicity. Toxic chemicals with relative toxicity of 50 mg/kg <strong>and</strong> below are considered highly toxic <strong>and</strong> those with<strong>in</strong> the 50–500 mg/kg range are generally considered moderately toxic. Some examples follow: Highly toxic chemicals (0–50 mg/kg) Moderately toxic chemicals (50–500 mg/kg) Botul<strong>in</strong>um tox<strong>in</strong> 0.00001 (= 10 ng) Paraquat 95 Diox<strong>in</strong> 0.1 Caffe<strong>in</strong>e 200 Parathion 13.0 Carbaryl 270 Strychn<strong>in</strong>e 30.0 Malathion 370 Nicot<strong>in</strong>e 50.0 2,4-dichlorophenoxyacetic acid 375 Brief history of <strong>in</strong>secticide usage <strong>in</strong> pest control A brief history of <strong>in</strong>secticide usage <strong>in</strong> the control of <strong>in</strong>sect pests appears <strong>in</strong> Table 2.1. It should be po<strong>in</strong>ted out that, up to 1950, the dom<strong>in</strong>ant <strong>in</strong>secticide used was arsenic-based. With the discovery of DDT as a potent <strong>in</strong>secticide after World War II, organochlor<strong>in</strong>es were ma<strong>in</strong>ly used for <strong>in</strong>sect control until they were replaced by organophosphates <strong>and</strong> carbamates by 1975. Pyrethr<strong>in</strong>s extracted from plants were effective <strong>in</strong>secticides but were quickly degraded by UV (ultraviolet) light <strong>in</strong> the fi eld <strong>and</strong> thus were <strong>in</strong>effective as agricultural <strong>in</strong>secticides. Based on the pyrethr<strong>in</strong> molecule, a pyrethroid, permethr<strong>in</strong> (stable under UV light), was discovered <strong>and</strong> synthetized specifi cally for use <strong>in</strong> agriculture <strong>in</strong> the late 1970s. In the early 1980s, several pyrethroids began to be used widely. Because of the widespread use of organochlor<strong>in</strong>es, organophosphates, carbamates, <strong>and</strong> pyrethroids, <strong>in</strong>secticide resistance (cross- <strong>and</strong> multiple-resistance) developed <strong>in</strong> many species of <strong>in</strong>sect pests. <strong>Insecticide</strong> resistance renders many <strong>in</strong>secticides <strong>in</strong>effective as a control measure. Consequently, many chemical companies <strong>in</strong>volved <strong>in</strong> the manufactur<strong>in</strong>g of <strong>in</strong>secticides have been replac<strong>in</strong>g them with new <strong>and</strong> less toxic chemicals. <strong>Research</strong> methods <strong>in</strong> toxicology <strong>and</strong> <strong>in</strong>secticide resistance monitor<strong>in</strong>g of rice planthoppers 21
- Page 2 and 3: Research Methods in Toxicology and
- Page 4 and 5: Contents Foreword v Preface vii Ack
- Page 6: Foreword By 2020, the world will re
- Page 9 and 10: synergistic, antagonistic, or no ad
- Page 11 and 12: CHAPTER 1: Introduction to insect t
- Page 13 and 14: Toxicology (derived from two Greek
- Page 15 and 16: ogy can be subdivided into many sub
- Page 17 and 18: Step 8: 3-phosphoglycerate is isome
- Page 19 and 20: Each pyruvate molecule when complet
- Page 21 and 22: H + H + H + H + NADH Cytochrome c d
- Page 23 and 24: Insect physiology Mitochondria A mi
- Page 25 and 26: of sodium channels allowing sodium
- Page 27 and 28: ) Cytosol Pretranslation Masking, d
- Page 29: CHAPTER 2: Insecticide toxicology R
- Page 33 and 34: 2. Application technique, for examp
- Page 35 and 36: nant in insects. In the neurons, th
- Page 37 and 38: 30 g/kg, and fenoxycarb, LD 50 16.8
- Page 39 and 40: tive feedback of acetylcholine rele
- Page 41 and 42: Metabolic resistance via detoxifica
- Page 43 and 44: 5. pen—a recessive gene that decr
- Page 45 and 46: 1. Use of an appropriate synergist,
- Page 47 and 48: CHAPTER 3: Quantal response data an
- Page 49 and 50: Insecticide research generally invo
- Page 51 and 52: esponse to probits is available in
- Page 53 and 54: CHAPTER 4: Rearing and preparation
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- Page 57 and 58: 4.3 4.4 Fig. 4.3. Aluminum rearing/
- Page 59 and 60: Preparation of standardized test in
- Page 61 and 62: CHAPTER 5: Preparation of test solu
- Page 63 and 64: The median lethal dose (LD 50 ) of
- Page 65 and 66: Fig. 5.3. Recovery cage preparation
- Page 67 and 68: Fig. 5.6. Treated planthoppers are
- Page 69 and 70: CHAPTER 6: Analyz ing quantal respo
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- Page 73 and 74: 3. There is a need to further forma
- Page 75 and 76: Using PoloPlus© The quantal respon
- Page 77 and 78: Fig. 6.1. Output results. Research
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The lethal dose ratio on lines 95-9
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8. Then, Paste the Excel data sets
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3. For the fi rst population, open
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5. Highlight and Copy the Probit va
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9. Right-click the y-axis, and clic
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CHAPTER 7: Analyzing joint action o
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PoloMix© is another software devel
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c. Lastly, on the File menu, the Sa
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Fig. 7.2. PoloMix© output. Researc
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CHAPTER 8: Presenting results Resea
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The previous chapters provide the m
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References Abbott WS. 1925. A metho
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Sudderudin KI, Tan KH. 1973. Some h
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Appendix A Table 1. Transformation
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Appendix Table B1. Raw data recordi
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Appendix C Table 1. The distributio