Insect growth regulator

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An insect growth regulator (IGR) is a type of chemical insecticide that disrupts the life cycle of insects rather than killing them directly. [1] The term was initially proposed to describe the effects of juvenile hormone analogs. [2] Although the term "insect growth disruptor" more accurately describes the actions of IGRs, it did not become widely used. [1] IGRs encompass three main chemical classes, each with a distinct mode of action; juvenile hormone analogs, chitin synthesis inhibitors, and ecdysone receptor agonists

Contents

Juvenile Hormone analogs

Juvenile hormone analogs are also known as juvenile hormone mimics, juvenoids, or JH signaling activators. [1] [3] Juvenile hormone (JH) controls many important processes in insects including metamorphosis. After the structure determination of the JHs in the 1960s, the search for more stable and useable analogs started. Zoecon introduced methoprene in 1975, and later hydroprene and kinoprene. Later again other companies introduced the more stable fenoxycarb and pyriproxyfen.

JH mimics sold for $87 million globally in 2018, which is a small proportion of the $18.4 billion insecticide market in 2018. [4] They are used against both sap-feeding and leaf eating insects as well as for vector control. [3]

They have low vertebrate and environmental toxicity. Methoprene and pyriproxyfen are recommended by the WHO for treating drinking water sources and containers. [5]

Many plants produce juvenile hormone mimics (phytojuvenoids) to kill insects. [6]

Chitin synthesis inhibitors

Chitin synthesis inhibitors work by preventing the formation of chitin, an important part of the insect's exoskeleton. The main class of chitin synthesis inhibitors are the benzoyl ureas (BPUs). [7] The first BPU, diflubenzuron, was commercialised by Phillips-Duphar in 1975. Since then, many BPUs were commercialised by many companies. BPUs accounted for 3% of the $18.4 billion world insecticide market in 2018. [4] They are active against types of insect pests, (e.g. lepidoptera coleoptera, diptera) in agriculture, [7] [1] as well as being used against termites and animal health pests such as fleas. [8] BPUs have low mammalian toxicity (Diflubenzuron is approved by the WHO for treatment of drinking water as a mosquito larvicide [5] ) but they are highly toxic to water invertebrates and crustaceans. [7] They disrupt moulting and egg hatch and act by inhibiting the enzyme chitin synthase. [9]

Other chemical classes of chitin synthesis inhibitors, were shown to also act through inhibition of chitin synthase: - buprofezine, [9] ethoxazole, [9] clofentazine, [10] hexythiazole, [10] and cyromazine. [11]

Ecdysone agonists

The only commercial class of ecdysone agonists are the bisacyl hydrazines (BAHs). [3] The first BAH to be commercialised was tebufenozide, discovered in the 1980s at Rohm & Haas, who later commercialised methoxyfenozide, and halofenozide. Later other companies commercialised chromafenozide and fufenozide. BAHs were estimated to account for ca 1% of the 18.4 billion dollar 2018 global pesticide market. [4] They produce premature unsuccessful moulting, and act by agonising the ecdysone receptor. [3] BAHs show low mamalian and environmental toxicity. Methoxyfenozide was given a presidential green chemistry award in 1998. Both tebufenozide and methoxyfenozide were registered by the EPA under its Reduced Risk Pesticide Program. [3] Many plants produce chemicals (phytoecdysteroids) which use this mode of action to kill insects.

Others

Azadirachtin (AzaGuard), a natural product found in extracts from the neem tree, shows antifeedant, repellent and insecticidal activity. Many different symptoms and modes of action are observed including disruption of growth and moulting. [12]

Advantages and disadvantages

In general IGRs show low toxicity to mammals and non-target organisms. [1] However there are differences between the substance classes and the individual compounds. Some IGRs are labeled "reduced risk" by the Environmental Protection Agency, IGRs are also more compatible with pest management systems that use biological controls. [13] It was originally expected that insects would not be able to develop resistance to IGRs, [14] but this turned out not to be the case. [1]

However they are slower to kill insects, show limited control of adult insects, and are in general more expensive that many other insecticides, [15]

Related Research Articles

<span class="mw-page-title-main">Insecticide</span> Pesticide used against insects

Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Acaricides, which kill mites and ticks, are not strictly insecticides, but are usually classified together with insecticides. The major use of Insecticides is agriculture, but they are also used in home and garden, industrial buildings, vector control and control of insect parasites of animals and humans. Insecticides are claimed to be a major factor behind the increase in the 20th-century's agricultural productivity. Nearly all insecticides have the potential to significantly alter ecosystems; many are toxic to humans and/or animals; some become concentrated as they spread along the food chain.

<span class="mw-page-title-main">Azadirachtin</span> Chemical compound

Azadirachtin, a chemical compound belonging to the limonoid group, is a secondary metabolite present in neem seeds. It is a highly oxidized tetranortriterpenoid which boasts a plethora of oxygen-bearing functional groups, including an enol ether, acetal, hemiacetal, tetra-substituted epoxide and a variety of carboxylic esters.

<span class="mw-page-title-main">Piperonyl butoxide</span> Chemical compound

Piperonyl butoxide (PBO) is a pale yellow to light brown liquid organic compound used as an adjuvant component of pesticide formulations for synergy. That is, despite having no pesticidal activity of its own, it enhances the potency of certain pesticides such as carbamates, pyrethrins, pyrethroids, and rotenone. It is a semisynthetic derivative of safrole and is produced from the condensation of the sodium salt of 2-(2-butoxyethoxy) ethanol and the chloromethyl derivative of hydrogenated safrole (dihydrosafrole). Although this route of synthesis has faced a lot of criticism in recent times. The new route of synthesis is through 1,2-Methylenedioxybenzene, developed by The Anthea Group and patented in 2019.

Juvenile hormones (JHs) are a group of acyclic sesquiterpenoids that regulate many aspects of insect physiology. The first discovery of a JH was by Vincent Wigglesworth. JHs regulate development, reproduction, diapause, and polyphenisms.

<span class="mw-page-title-main">Carbamate</span> Chemical group (>N–C(=O)–O–)

In organic chemistry, a carbamate is a category of organic compounds with the general formula R2NC(O)OR and structure >N−C(=O)−O−, which are formally derived from carbamic acid. The term includes organic compounds, formally obtained by replacing one or more of the hydrogen atoms by other organic functional groups; as well as salts with the carbamate anion H2NCOO−.

<span class="mw-page-title-main">Neem oil</span> Vegetable oil from the Indian neem tree

Neem oil, also known as margosa oil, is a vegetable oil pressed from the fruits and seeds of the neem, a tree which is indigenous to the Indian subcontinent and has been introduced to many other areas in the tropics. It is the most important of the commercially available products of neem, and its chemical properties have found widespread use as a pesticide in organic farming.

<span class="mw-page-title-main">Methoprene</span> Chemical compound

Methoprene is a juvenile hormone (JH) analog which acts as a growth regulator when used as an insecticide. It is an amber-colored liquid with a faint fruity odor.

<span class="mw-page-title-main">Fenoxycarb</span> Chemical compound

Fenoxycarb is a carbamate insect growth regulator. It has a low toxicity for bees, birds, and humans, but is toxic to fish. The oral LD50 for rats is greater than 16,800 milligrams per kilogram (0.269 oz/lb).

<span class="mw-page-title-main">Pyriproxyfen</span> Chemical compound

Pyriproxyfen is a pesticide which is found to be effective against a variety of insects. It was introduced to the US in 1996, to protect cotton crops against whitefly. It has also been found useful for protecting other crops. It is also used as a prevention for flea control on household pets, for killing indoor and outdoor ants and roaches. Methods of application include aerosols, bait, carpet powders, foggers, shampoos and pet collars.

Phytotoxins are substances that are poisonous or toxic to the growth of plants. Phytotoxic substances may result from human activity, as with herbicides, or they may be produced by plants, by microorganisms, or by naturally occurring chemical reactions.

<span class="mw-page-title-main">Phenothrin</span> Chemical compound

Phenothrin, also called sumithrin and d-phenothrin, is a synthetic pyrethroid that kills adult fleas and ticks. It has also been used to kill head lice in humans. d-Phenothrin is used as a component of aerosol insecticides for domestic use. It is often used with methoprene, an insect growth regulator that interrupts the insect's biological lifecycle by killing the eggs.

<span class="mw-page-title-main">Benzoylurea</span> Chemical compound

Benzoylureas (BPUs) are chemical derivatives of N-benzoyl-N′-phenylurea, which are used as insecticides. They do not directly kill the insect, but disrupt moulting and egg hatch, and thus act as insect growth regulators. They act by inhibiting chitin synthase, preventing the formation of chitin in the insect's body.

<span class="mw-page-title-main">Juvenile-hormone esterase</span>

The enzyme juvenile hormone esterase (EC 3.1.1.59, systematic name methyl-(2E,6E,10R)-10,11-epoxy-3,7,11-trimethyltrideca-2,6-dienoate acylhydrolase, JH esterase) catalyzes the hydrolysis of juvenile hormone:

<span class="mw-page-title-main">Ecdysone receptor</span>

The ecdysone receptor is a nuclear receptor found in arthropods, where it controls development and contributes to other processes such as reproduction. The receptor is a non-covalent heterodimer of two proteins, the EcR protein and ultraspiracle protein (USP). It binds to and is activated by ecdysteroids. Insect ecdysone receptors are currently better characterized than those from other arthropods, and mimics of ecdysteroids are used commercially as caterpillar-selective insecticides.

<span class="mw-page-title-main">Diflubenzuron</span> Chemical compound

Diflubenzuron is an insecticide of the benzoylurea class. It is used in forest management and on field crops to selectively control insect pests, particularly forest tent caterpillar moths, boll weevils, gypsy moths, and other types of moths. It is a widely used larvicide in India for control of mosquito larvae by public health authorities. Diflubenzuron is approved by the WHO Pesticide Evaluation Scheme.

<span class="mw-page-title-main">Tebufenozide</span> Chemical compound

Tebufenozide is an insecticide that acts as a molting hormone. It is an agonist of the ecdysone receptor that causes premature molting in larvae. It is primarily used against caterpillar pests. It belongs to the class of bisacylhydrazines.

<span class="mw-page-title-main">Novaluron</span> Chemical compound

Novaluron, or (±)-1-[3-chloro-4-(1,1,2-trifluoro-2-trifluoro- methoxyethoxy)phenyl]-3-(2,6-difluorobenzoyl)urea, is a chemical with pesticide properties, belonging to the class of insecticides called insect growth regulators. It is a benzoylphenyl urea developed by Makhteshim-Agan Industries Ltd.. In the United States, the compound has been used on food crops, including apples, potatoes, brassicas, ornamentals, and cotton. Patents and registrations have been approved or are ongoing in several other countries throughout Europe, Asia, Africa, South America, and Australia. The US Environmental Protection Agency and the Canadian Pest Management Regulatory Agency consider novaluron to pose low risk to the environment and non-target organisms and value it as an important option for integrated pest management that should decrease reliance on organophosphorus, carbamate and pyrethroid insecticides.

<span class="mw-page-title-main">Buprofezin</span> Chemical compound

Buprofezin is an insecticide used for control of insect pests such as mealybugs, leafhoppers and whitefly on vegetable crops. It is a growth regulator, acting as an inhibitor of chitin synthesis. It is banned in some countries due to its negative environmental impacts, being especially toxic to aquatic organisms as well as non-target insects, though is of low toxicity to humans and other mammals.

<span class="mw-page-title-main">Dibenzoylhydrazine</span> Chemical compound

Dibenzoylhydrazine (DBH) is a synthetic chemical compound with the chemical formulation C14H12N2O2.

<span class="mw-page-title-main">Nereistoxin</span> Chemical compound

Nereistoxin is a natural product identified in 1962 as the toxic organic compound N,N-dimethyl-1,2-dithiolan-4-amine. It had first been isolated in 1934 from the marine annelid Lumbriconereis heteropoda and acts by blocking the nicotinic acetylcholine receptor. Researchers at Takeda in Japan investigated it as a possible insecticide. They subsequently developed a number of derivatives that were commercialised, including those with the ISO common names bensultap, cartap, thiocyclam and thiosultap.

References

  1. 1 2 3 4 5 6 Pener, Meir Paul; Dhadialla, Tarlochan S. (2012). "An Overview of Insect Growth Disruptors; Applied Aspects". Insect Growth Disruptors. Advances in Insect Physiology. Vol. 43. Oxford: Academic Press. pp. 1–162. doi:10.1016/B978-0-12-391500-9.00001-2. ISBN   978-0-12-391500-9. ISSN   0065-2806.
  2. ↑ Schneiderman, Howard A. (1972). "Insect hormones and insect control". In Menn, Julius J.; Beroza, Morton (eds.). Insect Juvenile Hormones: Chemistry and Action. New York: Academic Press. pp. 3–27. doi:10.1016/B978-0-12-490950-2.50001-2. ISBN   978-0-12-490950-2.
  3. 1 2 3 4 5 Jeschke, Peter; Witschel, Matthias; Krämer, Wolfgang; Schirmer, Ulrich (2019). "Chapter 29. Insect Molting and Metamorphosis". Modern Crop Protection Compounds. Wiley. pp. 1013–1065. doi:10.1002/9783527699261.ch29. ISBN   9783527699261.
  4. 1 2 3 Sparks, Thomas C.; Crossthwaite, Andrew J.; Nauen, Ralf; Banba, Shinichi; Cordova, Daniel; Earley, Fergus; Ebbinghaus-Kintscher, Ulrich; Fujioka, Shinsuke; Hirao, Ayako; Karmon, Danny; Kennedy, Robert; Nakao, Toshifumi; Popham, Holly J.R.; Salgado, Vincent; Watson, Gerald B. (2020). "Insecticides, biologics and nematicides: Updates to IRAC's mode of action classification - a tool for resistance management". Pesticide Biochemistry and Physiology. 167: 104587. Bibcode:2020PBioP.16704587S. doi: 10.1016/j.pestbp.2020.104587 . PMID   32527435.
  5. 1 2 Guidelines for drinking-water quality: fourth edition incorporating the first addendum (4th ed.). Geneva: World Health Organization. 2017. pp. 434–441. ISBN   978-92-4-154995-0.
  6. ↑ Bede, Jacqueline C.; Tobe, Stephen S. (2000). "Insect Juvenile Hormones in Plants". Studies in Natural Products Chemistry. 22, Part C: 369–418. doi:10.1016/S1572-5995(00)80031-9. ISBN   978-0-444-50588-0. ISSN   1572-5995 – via Elsevier.
  7. 1 2 3 Sun, Ranfeng; Liu, Chunjuan; Hao, Zhang; Wang, Qingmin (July 13, 2015). "Benzoylurea Chitin Synthesis Inhibitors". J. Agric. Food Chem. 63 (31): 6847–6865. doi:10.1021/acs.jafc.5b02460. PMID   26168369.
  8. ↑ Junquera, Pablo; Hosking, Barry; Gameiro, Marta; Macdonald, Alicia (2019). "Benzoylphenyl ureas as veterinary antiparasitics. An overview and outlook with emphasis on efficacy, usage and resistance". Parasite. 26: 26. doi:10.1051/parasite/2019026. ISSN   1776-1042. PMC   6492539 . PMID   31041897. Open Access logo PLoS transparent.svg
  9. 1 2 3 Douris, Vassilis; Steinbach, Denise; Panteleri, Rafaela; Livadaras, Ioannis; Pickett, John Anthony; Van Leeuwen, Thomas; Nauen, Ralf; Vontas, John (2016). "2016". Proceedings of the National Academy of Sciences. 113 (51): 14692–14697. doi: 10.1073/pnas.1618258113 . PMC   5187681 . PMID   27930336.
  10. 1 2 Demaeght, Peter; Osborne, Edward J.; Odman-Naresh, Jothini; Grbić, Miodrag; Nauen, Ralf; Merzendorfer, Hans; Clark, Richard M.; Van Leeuwen, Thomas (2014). "High resolution genetic mapping uncovers chitin synthase-1 as the target-site of the structurally diverse mite growth inhibitors clofentezine, hexythiazox and etoxazole in Tetranychus urticae". Insect Biochemistry and Molecular Biology. 51: 52–61. Bibcode:2014IBMB...51...52D. doi:10.1016/j.ibmb.2014.05.004. ISSN   0965-1748. PMC   4124130 . PMID   24859419.
  11. ↑ Zeng, Bin; Chen, Fu-Rong; Liu, Ya-Ting (2022). "A chitin synthase mutation confers widespread resistance to buprofezin, a chitin synthesis inhibitor, in the brown planthopper, Nilaparvata lugens". Journal of Pest Science. 96 (2): 819–832. doi:10.1007/s10340-022-01538-9.
  12. ↑ Kilani-Morakchi, Samira; Morakchi-Goudjil, Houda; Sifi, Karima (20 July 2021). "Azadirachtin-Based Insecticide: Overview, Risk Assessments, and Future Directions". Frontiers in Agronomy. 3: 676208. doi: 10.3389/fagro.2021.676208 .
  13. ↑ Krysan, James; Dunley, John. "Insect Growth Regulators". Archived from the original on 30 November 2021. Retrieved 20 November 2010.
  14. ↑ Williams, Carroll.M., Carroll.M. (1967). "Third-generation pesticides". Scientific American. 217 (1): 13–17. Bibcode:1967SciAm.217a..13W. doi:10.1038/scientificamerican0767-13. PMID   6046326.
  15. ↑ Kumar, Ravendra, ed. (2024). "Chapter 4. Role of insect growth regulators in insect/pest control". Biorationals and Biopesticides. Berlin/Boston: Walter de Gruyter. pp. 77–94. ISBN   978-3-11-120472-7.
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