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Insecticide

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Title: Insecticide  
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Insecticide

FLIT manual spray pump for insecticides from 1928

An insecticide is a substance used to kill insects.[1] They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to be a major factor behind the increase in agricultural 20th century's productivity.[2] Nearly all insecticides have the potential to significantly alter ecosystems; many are toxic to humans; some concentrate along the food chain.

Insecticides can be classified in two major groups as systemic insecticide which have residual or long term activity and contact insecticides, which have no residual activity.

Furthermore, one can distinguish natural insecticides, such as nicotine, pyrethrum and neem extracts, made by plants as defenses against insects, inorganic insecticides, which are metals, versus organic insecticides, which are organic chemical compounds mostly working by contact.

The mode of action describes how the pesticide kills or inactivates a pest. It provides another way of classifying insecticides. Mode of action is important in understanding whether an insecticide will be toxic to unrelated species, such as fish, birds and mammals.

For products that repel rather than kill insects see insect repellents.

Contents

  • Type of activity 1
  • Major classes 2
    • Organochlorides 2.1
    • Organophosphates and carbamates 2.2
    • Pyrethroids 2.3
    • Neonicotinoids 2.4
    • Ryanoids 2.5
    • Plant-incorporated protectants 2.6
    • Biological 2.7
      • Bacterial 2.7.1
  • Insect growth regulators 3
  • Environmental effects 4
    • Effects on nontarget species 4.1
    • DDT 4.2
    • Pollinator decline 4.3
  • Individual insecticides 5
    • Organochloride 5.1
    • Organophosphate 5.2
    • Carbamate 5.3
    • Pyrethroid 5.4
    • Neonicotinoid 5.5
    • Ryanoid 5.6
    • Insect growth regulators 5.7
    • Plant-derived 5.8
    • Biologicals 5.9
    • Other 5.10
  • See also 6
  • References 7
  • Further reading 8
  • External links 9

Type of activity

Systemic insecticides become incorporated and distributed systemically throughout the whole plant. When insects feed on the plant, they ingest the insecticide. Systemic insecticides produced by transgenic plants are called plant-incorporated protectants (PIPs). For instance, a gene that codes for a specific Bacillus thuringiensis biocidal protein was introduced into corn and other species. The plant manufactures the protein, which kills the insect when consumed.[3] Systemic insecticides have activity pertaining to their residue which is called "residual activity" or long-term activity.

Contact insecticides are toxic to insects upon direct contact. These can be inorganic insecticides, which are metals and include arsenates, copper and fluorine compounds, which are less commonly used, and the commonly used sulfur. Contact insecticides can be organic insecticides, i.e. organic chemical compounds, synthetically produced, and comprising the largest numbers of pesticides used today. Or they can be natural compounds like pyrethrum, neem oil etc. Contact insecticides usually have no residual activity.

Efficacy can be related to the quality of pesticide application, with small droplets, such as aerosols often improving performance.[4]

Major classes

Organochlorides

The best known organochloride, DDT, was created by Swiss scientist Paul Müller. For this discovery, he was awarded the 1948 Nobel Prize for Physiology or Medicine.[5] DDT was introduced in 1944. It functions by opening sodium channels in the insect's nerve cells.[6] The contemporaneous rise of the chemical industry facilitated large-scale production of DDT and related chlorinated hydrocarbons.

Organophosphates and carbamates

environmentally friendly than synthetic pesticides. The toxin from B. thuringiensis (Bt toxin) has been incorporated directly into plants through the use of genetic engineering. Other biological insecticides include products based on entomopathogenic fungi (e.g., Beauveria bassiana, Metarhizium anisopliae), nematodes (e.g., Steinernema feltiae) and viruses (e.g., Cydia pomonella granulovirus).

Insect growth regulators

cisterns to combat malaria. Most of its uses are to combat insects where the adult is the pest, including mosquitoes, several fly species, and fleas. Two very similar products, hydroprene and kinoprene, are used for controlling species such as cockroaches and white flies. Methoprene was registered with the EPA in 1975. Virtually no reports of resistance have been filed. A more recent type of IGR is the ecdysone agonist tebufenozide (MIMIC), which is used in forestry and other applications for control of caterpillars, which are far more sensitive to its hormonal effects than other insect orders.

Environmental effects

Effects on nontarget species

Some insecticides kill or harm other creatures in addition to those they are intended to kill. For example, birds may be poisoned when they eat food that was recently sprayed with insecticides or when they mistake an insecticide granule on the ground for food and eat it.[7]

Sprayed insecticide may drift from the area to which it is applied and into wildlife areas, especially when it is sprayed aerially.[7]

DDT

The development of DDT was motivated by desire to replace more dangerous or less effective alternatives. DDT was introduced to replace lead and arsenic-based compounds, which were in widespread use in the early 1940s.[17]

DDT was brought to public attention by aldrin, chlordane, DDT, dieldrin, endrin, heptachlor, mirex and toxaphene.

Pollinator decline

Insecticides can kill bees and may be a cause of pollinator decline, the loss of bees that pollinate plants, and colony collapse disorder (CCD),[18] in which worker bees from a beehive or Western honey bee colony abruptly disappear. Loss of pollinators means a reduction in crop yields.[18] Sublethal doses of insecticides (i.e. imidacloprid and other neonicotinoids) affect bee foraging behavior.[19] However, research into the causes of CCD was inconclusive as of June 2007.[20]

Individual insecticides

Pyrethroids

Neonicotinoids

Ryanoids

Insect growth regulators

Plant-derived

Biologicals

Other

See also

References

  1. ^ IUPAC (2006). "GLOSSARY OF TERMS RELATING TO PESTICIDES" (PDF).  
  2. ^ van Emden, H.F.; Peakall, David B. (30 June 1996). Beyond Silent Spring. Springer.  
  3. ^ Plant Incorporated Protectants
  4. ^ "dropdata.org". dropdata.org. Retrieved 2011-01-05. 
  5. ^ Karl Grandin, ed. (1948). "Paul Müller Biography". Les Prix Nobel. The Nobel Foundation. Retrieved 2008-07-24. 
  6. ^ Vijverberg; et al. (1982). "Similar mode of action of pyrethroids and DDT on sodium channel gating in myelinated nerves". Nature 295 (295): 601.  
  7. ^ a b c Palmer, WE, Bromley, PT, and Brandenburg, RL. Wildlife & pesticides - Peanuts. North Carolina Cooperative Extension Service. Retrieved on 14 October 2007.
  8. ^ "Infographic: Pesticide Planet". Science 341 (6147): 730–731. 2013.  
  9. ^ Class, Thomas J.; Kintrup, J. (1991). "Pyrethroids as household insecticides: analysis, indoor exposure and persistence". Fresenius' Journal of Analytical Chemistry 340 (340): 446.  
  10. ^ Fishel,F.M. 2009. Pesticide Toxicity Profile: Neonicotinoid Pesticides IFAS Publication #PI-80
  11. ^ Insecticides taking toll on honeybees
  12. ^ Yao, Cheng; Shi, Zhao-Peng; Jiang, Li-Ben; Ge, Lin-Quan; Wu, Jin-Cai; Jahn, Gary C. (20 January 2012). "Possible connection between imidacloprid-induced changes in rice gene transcription profiles and susceptibility to the brown plant hopper Nilaparvata lugens Stål (Hemiptera: Delphacidae)". Pesticide Biochemistry and Physiology, 102 (3): 213–219.  
  13. ^ "Pesticide Fact Sheet- chlorantraniliprole" (PDF). http://www.epa.gov/opprd001/factsheets/chloran.pdf. Retrieved 2011-09-14. 
  14. ^ Kupferschmidt, K. (2013). "A Lethal Dose of RNA". Science 341 (6147): 732–3.  
  15. ^ Cole Rosemary A (1976). "Isothiocyanates, nitriles and thiocyanates as products of autolysis of glucosinolates in Cruciferae". Phytochemutry 15: 759–762.  
  16. ^ Trapp, S.; Croteau, R. (2001). "Defensive Biosynthesis of Resin in Conifers". Annual Review of Plant Physiology and Plant Molecular Biology 52 (1): 689–724.  
  17. ^ Metcalf, Robert L. (2002). "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann’s Encyclopedia of Industrial Chemistry (Wiley-VCH).  
  18. ^ a b Wells M (March 11, 2007). "Vanishing bees threaten US crops". www.bbc.co.uk (BBC News). Retrieved 19 September 2007. 
  19. ^ Colin, M. E.; Bonmatin, J. M.; Moineau, I.; et al. (2004). "A method to quantify and analyze the foraging activity of honey bees: Relevance to the sublethal effects induced by systemic insecticides". Archives of Environmental Contamination and Toxicology 47 (3): 387–395.  
  20. ^ Oldroyd, B.P. (2007). "What's Killing American Honey Bees?". PLoS Biology 5 (6): e168.  
  21. ^ a b c d "Cinnamon Oil Kills Mosquitoes". www.sciencedaily.com. Retrieved 5 August 2008. 
  22. ^ "Cornelia Dick-Pfaff: Wohlriechender Mückentod, 19.07.2004". 
  23. ^ "Oregano Oil Works As Well As Synthetic Insecticides To Tackle Common Beetle Pest". www.sciencedaily.com. Retrieved 23 May 2008. 
  24. ^ "Almond farmers seek healthy bees". BBC News. 2006-03-08. Retrieved 2010-01-05. 

Further reading

  • McWilliams, James E., "‘The Horizon Opened Up Very Greatly’: Leland O. Howard and the Transition to Chemical Insecticides in the United States, 1894–1927," Agricultural History, 82 (Fall 2008), 468–95.

External links

  • InsectBuzz.com - Daily updated news on insects and their relatives, including information on insecticides and their alternatives
  • International Pesticide Application Research Centre (IPARC)
  • Pestworld.org – Official site of the National Pest Management Association
  • Classification of insecticides
  • Streaming online video about efforts to reduce insecticide use in rice in Bangladesh. on Windows Media Player, on RealPlayer
  • How Insecticides Work – Has a thorough explanation on how insecticides work.
  • University of California Integrated pest management program
  • Using Insecticides, Michigan State University Extension
  • Example of Insecticide application in the Tsubo-en Zen garden (Japanese dry rock garden) in Lelystad, The Netherlands.

Bacterial

In general, tree rosin is considered a natural insecticide. To be specific, the production of oleoresin by conifer species is a component of the defense response against insect attack and fungal pathogen infection.[16]

The myrosinase is released only upon crushing the flesh of horseradish. Since allyl isothiocyanate is harmful to the plant as well as the insect, it is stored in the harmless form of the glucosinolate, separate from the myrosinase enzyme.[15]

Biosynthesis of antifeedants by the action of myrosinase.

Many plants exude substances to repel insects. Premier examples are substances activated by the enzyme myrosinase. This enzyme converts glucosinolates to various compounds that are toxic to herbivorous insects. One product of this enzyme is allyl isothiocyanate, the pungent ingredient in horseradish sauces.

Biological

Transgenic crops that act as insecticides began in 1996 with a genetically modified potato that produced the Cry protein, derived from the bacterium Bacillus thuringiensis, which is toxic to beetle larvae such as the Colorado potato beetle. The technique has been expanded to include the use of RNA interference RNAi that fatally silences crucial insect genes. RNAi likely evolved as a defense against viruses. Midgut cells in many larvae take up the molecules and help spread the signal. The technology can target only insects that have the silenced sequence, as was demonstrated when a particular RNAi affected only one of four fruit fly species. The technique is expected to replace many other insecticides, which are losing effectiveness due to the spread of pesticide resistance.[14]

Plant-incorporated protectants

Ryanoids are synthetic analogues with the same mode of action as ryanodine, a naturally occurring insecticide extracted from Ryania speciosa (Flacourtiaceae). They bind to calcium channels in cardiac and skeletal muscle, blocking nerve transmission. Only one such insecticide is currently registered, Rynaxypyr, generic name chlorantraniliprole.[13]

Ryanoids

Neonicotinoids are synthetic analogues of the natural insecticide nicotine (with much lower acute mammalian toxicity and greater field persistence). These chemicals are acetylcholine receptor agonists. They are broad-spectrum systemic insecticides, with rapid action (minutes-hours). They are applied as sprays, drenches, seed and soil treatments. Treated insects exhibit leg tremors, rapid wing motion, stylet withdrawal (aphids), disoriented movement, paralysis and death.[10] Imidacloprid may be the most common. It has recently come under scrutiny for allegedly pernicious effects on honeybees[11] and its potential to increase the susceptibility of rice to planthopper attacks.[12]

Neonicotinoids

applied against household pests.[9]

Pyrethroids

Carbamate insecticides have similar mechanisms to organophosphates, but have a much shorter duration of action and are somewhat less toxic.

[8]

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