Editing Insecticide (section)

==Synthetic insecticides==
Insecticides are most usefully categorised according to their [[Mode of action|modes of action]]. The [[Insecticide Resistance Action Committee|insecticide resistance action committee]] (IRAC) lists 30 modes of action plus unknowns. There can be several [[Insecticide Resistance Action Committee#Classes of Insecticide|chemical classes]] of insecticide with the same mode or action. IRAC lists 56 chemical classes plus unknowns.

The [[mode of action]] describes how the insecticide kills or inactivates a pest.

=== Development ===
{{main|pesticide#Development of new pesticides}}Insecticides with systemic activity against sucking pests, which are safe to [[Pollinator|pollinators]], are sought after,<ref>{{Cite journal |last=Sparks |first=Thomas |date=August 2022 |title=Innovation in insecticide discovery: Approaches to the discovery of new classes of insecticides |journal=Pest Management Science |volume=78 |issue=8 |pages=3226–3247 |doi=10.1002/ps.6942 |pmid=35452182 |s2cid=248322585}}</ref><ref name=":02">{{Cite journal |last=Sparks |first=Thomas |date=May 2023 |title=Insecticide discovery–"Chance favors the prepared mind" |journal=Pesticide Biochemistry and Physiology |volume=192 |pages=105412 |doi=10.1016/j.pestbp.2023.105412 |pmid=37105622 |bibcode=2023PBioP.19205412S |s2cid=257790593}}</ref><ref name=":15">{{Cite journal |last=Umetsu |first=Noriharu |date=May 2020 |title=Development of novel pesticides in the 21st century |journal=Journal of Pesticide Science |volume=45 |issue=2 |pages=54–74 |doi=10.1584/jpestics.D20-201 |pmc=7581488 |pmid=33132734}}</ref> particularly in view of the partial bans on [[Neonicotinoid|neonicotinoids]]. Revised 2023 guidance by registration authorities describes the bee testing that is required for new insecticides to be approved for commercial use.<ref>{{Cite web |date=11 May 2023 |title=Bees and pesticides: updated guidance for assessing risks |url=https://www.efsa.europa.eu/en/news/bees-and-pesticides-updated-guidance-assessing-risks |access-date=26 Nov 2023 |website=European Food Safety Authority}}</ref><ref>{{Cite journal |last=Adriaanse |first=Pauline |date=11 May 2023 |title=Revised guidance on the risk assessment of plant protection products on bees (Apis mellifera, Bombus spp. and solitary bees) |journal=EFSA Journal |volume=21 |issue=5 |pages=7989 |doi=10.2903/j.efsa.2023.7989 |pmc=10173852 |pmid=37179655}}</ref><ref>{{Cite web |date=28 June 2023 |title=How We Assess Risks to Pollinators |url=https://www.epa.gov/pollinator-protection/how-we-assess-risks-pollinators |website=United States Environmental Protection Agency}}</ref><ref>{{Cite web |title=Managing Pesticide Risk to Insect Pollinators; Laws, Policies and Guidance |url=https://www.oecd.org/chemicalsafety/risk-mitigation-pollinators/laws-policies-guidance.htm |access-date=28 Nov 2023 |website=Organisation for Economic Cooperation and Development}}</ref>

=== Systemicity and translocation ===
Insecticides may be systemic or non-systemic (contact insecticides).<ref name=":0" /><ref name=":1">{{cite journal |last1=Zhang |first1=Y |last2=Lorsbach |first2=BA |last3=Castetter |first3=S |last4=Lambert |first4=WT |last5=Kister |first5=J |last6=Wang |first6=N |date=2018 |title=Physicochemical property guidelines for modern agrochemicals |journal=Pest Management Science |volume=74 |issue=9 |page=1979-1991 |doi=10.1002/ps.5037 |pmid=29667318 |s2cid=4937939}}</ref><ref name=":4">{{cite journal |last1=Hofstetter |first1=S |date=2018 |title=How To Design for a Tailored Subcellular Distribution of Systemic Agrochemicals in Plant Tissues |url=https://backend.orbit.dtu.dk/ws/files/167227061/Rev_Hofstetter_et_al_intracellular_localization_of_agrochemicals.pdf |journal=J. Agric. Food Chem. |volume=66 |issue=33 |pages=8687–8697 |doi=10.1021/acs.jafc.8b02221 |pmid=30024749 |bibcode=2018JAFC...66.8687H |s2cid=261974999}}</ref> Systemic insecticides penetrate into the plant and move (translocate) inside the plant. Translocation may be upward in the [[xylem]], or downward in the [[phloem]] or both. Systemicity is a prerequisite for the pesticide to be used as a [[Seed treatment|seed-treatment]]. Contact insecticides (non-systemic insecticides) remain on the leaf surface and act through direct contact with the insect.

[[Eating behavior in insects|Insects feed]] from various compartments in the plant. Most of the major pests are either chewing insects or sucking insects.<ref>{{Cite web |last=Cloyd |first=Raymond A. |date=10 May 2022 |title=Insect and Mite Pests Feeding Behaviors and Plant Damage |url=https://gpnmag.com/article/dr-bugs-insect-and-mite-pests-feeding-behaviors-and-plant-damage |access-date=3 November 2024 |website=Greenhouse Product News}}</ref> Chewing insects, such as caterpillars, eat whole pieces of leaf. Sucking insects use feeding tubes to feed from phloem (e.g. aphids, leafhoppers, scales and whiteflies), or to suck cell contents (e.g. thrips and mites). An insecticide is more effective if it is in the compartment the insect feeds from. The physicochemical properties of the insecticide determine how it is distributed throughout the plant.<ref name=":1" /><ref name=":4" />

=== Organochlorides ===
The best known [[organochloride]], [[DDT]], was created by Swiss scientist [[Paul Hermann Müller|Paul Müller]]. For this discovery, he was awarded the 1948 [[Nobel Prize for Physiology or Medicine]].<ref>{{cite web |editor=Karl Grandin | title=Paul Müller Biography | url=http://nobelprize.org/nobel_prizes/medicine/laureates/1948/muller-bio.html | work=Les Prix Nobel | publisher=The Nobel Foundation | year=1948 | access-date=2008-07-24}}</ref> DDT was introduced in 1944. It functions by opening [[sodium channel]]s in the insect's [[nerve cell]]s.<ref>{{Cite journal |author=Vijverberg |title=Similar mode of action of pyrethroids and DDT on sodium channel gating in myelinated nerves |journal=Nature |volume=295 |issue=5850 |pages=601–603 |year=1982 |display-authors=1 |bibcode=1982Natur.295..601V |last2=Van Den Bercken |first2=Joep |doi=10.1038/295601a0|pmid=6276777 |s2cid=4259608 }}</ref> The contemporaneous rise of the chemical industry facilitated large-scale production of [[chlorinated hydrocarbon]]s including various [[cyclodiene]] and [[hexachlorocyclohexane]] compounds. Although commonly used in the past, many older chemicals have been removed from the market due to their health and environmental effects (''e.g.'' [[DDT]], [[chlordane]], and [[toxaphene]]).<ref>{{Cite web |date=Sep 2002 |title=Public Health Statement for DDT, DDE, and DDD |url=https://www.atsdr.cdc.gov/ToxProfiles/tp35-c1-b.pdf |url-status=live |archive-url=https://web.archive.org/web/20080923121618/http://www.atsdr.cdc.gov/toxprofiles/tp35-c1-b.pdf |archive-date=2008-09-23 |access-date=Dec 9, 2018 |website=atsdr.cdc.gov |publisher=[[Agency for Toxic Substances and Disease Registry|ATSDR]]}}</ref><ref>{{Cite web |date=Apr 18, 2012 |title=Medical Management Guidelines (MMGs): Chlordane |url=https://www.atsdr.cdc.gov/MMG/MMG.asp?id=349&tid=62 |access-date=Dec 9, 2018 |website=atsdr.cdc.gov |publisher=[[Agency for Toxic Substances and Disease Registry|ATSDR]]}}</ref>

=== Organophosphates ===
[[Organophosphate]]s are another large class of contact insecticides.  These also target the insect's nervous system. Organophosphates interfere with the [[enzyme]]s [[acetylcholinesterase]] and other [[cholinesterase]]s, causing an increase in synaptic [[acetylcholine]] and overstimulation of the [[parasympathetic nervous system]],<ref>{{cite journal |vauthors=Colović MB, Krstić DZ, Lazarević-Pašti TD, Bondžić AM, Vasić VM |date=May 2013 |title=Acetylcholinesterase inhibitors: pharmacology and toxicology |journal=Current Neuropharmacology |volume=11 |issue=3 |pages=315–35 |doi=10.2174/1570159X11311030006 |pmc=3648782 |pmid=24179466}}</ref> killing or disabling the insect. Organophosphate insecticides and [[chemical warfare]] [[Nerve agent|nerve agents]] (such as [[sarin]], [[Tabun (nerve agent)|tabun]], [[soman]], and [[VX (nerve agent)|VX]]) have the same mechanism of action. Organophosphates have a cumulative toxic effect to wildlife, so multiple exposures to the chemicals amplifies the toxicity.<ref name="palmerw"/> In the US, organophosphate use declined with the rise of substitutes.<ref name=s730>{{Cite journal | doi = 10.1126/science.341.6147.730 | title = Infographic: Pesticide Planet | journal = Science | volume = 341 | issue = 6147 | pages = 730–731 | year = 2013 | pmid =  23950524| bibcode = 2013Sci...341..730. }}</ref> Many of these insecticides, first developed in the mid 20th century, are very poisonous.<ref>{{Cite web |date=Aug 1996 |title=Toxicological Profile for Toxaphene |url=https://ntp.niehs.nih.gov/ntp/htdocs/chem_background/exsumpdf/toxaphene_508.pdf |access-date=Dec 9, 2018 |website=ntp.niehs.nih.gov |publisher=[[Agency for Toxic Substances and Disease Registry|ATSDR]] |pages=5}}</ref> Many [[Organophosphate|organophosphates]] do not persist in the environment.

=== Pyrethroids ===
[[Pyrethroid]] insecticides mimic the insecticidal activity of the natural compound [[pyrethrin]], the [[biopesticide]] found in ''[[Pyrethrum]]'' (Now ''[[Chrysanthemum]]'' and ''[[Tanacetum]]'') species. They have been modified to increase their stability in the environment. These compounds are nonpersistent sodium channel modulators and are less toxic than organophosphates and carbamates. Compounds in this group are often [[Pesticide application|applied against household pests]].<ref>{{Cite journal| last1=Class |first1=Thomas J. |last2=Kintrup |first2=J. | title=Pyrethroids as household insecticides: analysis, indoor exposure and persistence | journal=Fresenius' Journal of Analytical Chemistry |volume=340 | issue=7|pages=446–453 | year=1991 |doi=10.1007/BF00322420 |s2cid=95713100 }}</ref> Some synthetic pyrethroids are toxic to the nervous system.<ref>{{Cite book |last=Soderlund |first=David |title=Hayes' Handbook of Pesticide Toxicology |publisher=Academic Press |year=2010 |isbn=978-0-12-374367-1 |editor-last=Kreiger |editor-first=Robert |edition=3rd |pages=1665–1686 |chapter=Chapter 77 – Toxicology and Mode of Action of Pyrethroid Insecticides |oclc=918401061 |name-list-style=vanc}}</ref>

=== Neonicotinoids ===
[[Neonicotinoids]] are a class of neuro-active insecticides chemically similar to [[nicotine]].(with much lower acute mammalian toxicity and greater field persistence). These chemicals are [[acetylcholine]] receptor [[agonist]]s. 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 (anatomy)|stylet]] withdrawal ([[aphid]]s), disoriented movement, paralysis and death.<ref>{{cite web|url=http://edis.ifas.ufl.edu/pi117|title=Pesticide Toxicity Profile: Neonicotinoid Pesticides|first=Frederick M.|last=Fishel|date=9 March 2016|access-date=11 March 2012|archive-date=28 April 2007|archive-url=https://web.archive.org/web/20070428035003/http://edis.ifas.ufl.edu/PI117|url-status=dead}}</ref>[[Imidacloprid]], of the neonicotinoid family, is the most widely used insecticide in the world.<ref name="Yamamoto1999">{{cite book |last=Yamamoto |first=Izuru |title=Nicotinoid Insecticides and the Nicotinic Acetylcholine Receptor |publisher=Springer-Verlag |year=1999 |isbn=978-4-431-70213-9 |editor-last=Yamamoto |editor-first=Izuru |location=Tokyo |pages=3–27 |contribution=Nicotine to Nicotinoids: 1962 to 1997 |oclc=468555571 |editor2-last=Casida |editor2-first=John |editor2-link=John E. Casida |name-list-style=vanc}}</ref> In the late 1990s neonicotinoids came under increasing scrutiny over their environmental impact and were linked in a range of studies to adverse ecological effects, including [[honey-bee]] [[colony collapse disorder]] (CCD) and loss of birds due to a reduction in insect populations. In 2013, the [[European Union]] and a few non EU countries restricted the use of certain neonicotinoids.<ref>{{Cite journal |last=Cressey |first=D |date=2013 |title=Europe debates risk to bees |journal=Nature |volume=496 |issue=7446 |pages=408 |bibcode=2013Natur.496..408C |doi=10.1038/496408a |issn=1476-4687 |pmid=23619669 |doi-access=free}}</ref><ref>{{Cite journal |last1=Gill |first1=RJ |last2=Ramos-Rodriguez |first2=O |last3=Raine |first3=NE |date=2012 |title=Combined pesticide exposure severely affects individual- and colony-level traits in bees |journal=Nature |volume=491 |issue=7422 |pages=105–108 |bibcode=2012Natur.491..105G |doi=10.1038/nature11585 |issn=1476-4687 |pmc=3495159 |pmid=23086150}}</ref><ref>{{Cite journal |vauthors=Dicks L |date=2013 |title=Bees, lies and evidence-based policy |journal=Nature |volume=494 |issue=7437 |pages=283 |bibcode=2013Natur.494..283D |doi=10.1038/494283a |issn=1476-4687 |pmid=23426287 |doi-access=free}}</ref><ref>{{Cite journal |last=Stoddart |first=C |date=2012 |title=The buzz about pesticides |journal=Nature |doi=10.1038/nature.2012.11626 |issn=1476-4687 |s2cid=208530336 |doi-access=free}}</ref><ref>{{Cite journal |vauthors=Osborne JL |date=2012 |title=Ecology: Bumblebees and pesticides |journal=Nature |volume=491 |issue=7422 |pages=43–45 |bibcode=2012Natur.491...43O |doi=10.1038/nature11637 |issn=1476-4687 |pmid=23086148 |s2cid=532877}}</ref><ref>{{Cite journal |last=Cressey |first=D |date=2013 |title=Reports spark row over bee-bothering insecticides |journal=Nature |doi=10.1038/nature.2013.12234 |issn=1476-4687 |s2cid=88428354}}</ref><ref>{{Cite web |date=30 May 2013 |title=Bees & Pesticides: Commission goes ahead with plan to better protect bees |url=http://ec.europa.eu/food/animal/liveanimals/bees/neonicotinoids_en.htm |archive-url=https://web.archive.org/web/20130621042322/http://ec.europa.eu/food/animal/liveanimals/bees/neonicotinoids_en.htm |archive-date=21 June 2013}}</ref><ref>{{Cite web|url=http://www.columbiatribune.com/news/2012/feb/19/insecticides-taking-toll-on-honeybees/|archiveurl=https://web.archive.org/web/20120318005423/http://www.columbiatribune.com/news/2012/feb/19/insecticides-taking-toll-on-honeybees/|url-status=dead|title=Insecticides taking toll on honeybees|archivedate=March 18, 2012}}</ref> and its potential to increase the susceptibility of rice to [[planthopper]] attacks.<ref>{{cite journal |url=http://scienceindex.com/stories/2068471/Possible_connection_between_imidaclopridinduced_changes_in_rice_gene_transcription_profiles_and_susceptibility_to_the_brown_plant_hopperNilaparvatalugensStl_Hemiptera_Delphacidae.html |last1=Yao |first1=Cheng |first2=Zhao-Peng |last2=Shi |first3=Li-Ben |last3=Jiang |first4=Lin-Quan |last4=Ge |first5=Jin-Cai |last5=Wu |first6=Gary C. |last6=Jahn |title=Possible connection between imidacloprid-induced changes in rice gene transcription profiles and susceptibility to the brown plant hopper Nilaparvata lugens Stål (Hemiptera: Delphacidae) |journal=Pesticide Biochemistry and Physiology |volume=102 |issue=3 |pages=213–219 |date=20 January 2012 |issn=0048-3575 |doi=10.1016/j.pestbp.2012.01.003 |pmid=22544984 |pmc=3334832 |bibcode=2012PBioP.102..213C |url-status=dead |archive-url=https://web.archive.org/web/20130524213250/http://scienceindex.com/stories/2068471/Possible_connection_between_imidaclopridinduced_changes_in_rice_gene_transcription_profiles_and_susceptibility_to_the_brown_plant_hopperNilaparvatalugensStl_Hemiptera_Delphacidae.html |archive-date=24 May 2013 }}</ref>

=== Diamides ===
[[Diamide insecticide|Diamides]] selectively activate insect [[Ryanodine receptor|ryanodine receptors]] (RyR), which are large [[Calcium channel|calcium release channels]] present in cardiac and skeletal muscle,<ref name=":22">{{Cite book |last1=Nauen |first1=Ralf |title=Advances in Insect Control and Resistance Management |last2=Steinbach |first2=Denise |date=27 August 2016 |publisher=Springer |isbn=978-3-319-31800-4 |editor-last=Horowitz |editor-first=A. Rami |location=Cham |publication-date=26 August 2016 |pages=219–240 |chapter=Resistance to Diamide Insecticides in Lepidopteran Pests |doi=10.1007/978-3-319-31800-4_12 |editor-last2=Ishaaya |editor-first2=Isaac |chapter-url=https://doi.org/10.1007/978-3-319-31800-4_12}}</ref> leading to the loss of calcium crucial for biological processes. This causes insects to act lethargic, stop feeding, and eventually die.<ref name=":12">{{Cite journal |last1=Du |first1=Shaoqing |last2=Hu |first2=Xueping |date=February 15, 2023 |title=Comprehensive Overview of Diamide Derivatives Acting as Ryanodine Receptor Activators |url=https://pubs.acs.org/doi/abs/10.1021/acs.jafc.2c08414 |journal=Journal of Agricultural and Food Chemistry |volume=71 |issue=8 |pages=3620–3638 |doi=10.1021/acs.jafc.2c08414 |pmid=36791236|bibcode=2023JAFC...71.3620D }}</ref> The first insecticide from this class to be registered was [[flubendiamide]].<ref name=":12" />