Insect growth regulator

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An insect growth regulator (IGR) is a chemical insecticide that kills insects indirectly by disrupting their life cycles. [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 chemical classes with three modes of action (mechanisms 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. They are in IRAC group 7.

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 World Health Organization (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: buprofezin, [9] etoxazole, [9] clofentazine, [10] hexythiazole, [10] and cyromazine. [11] They are in IRAC mode of action groups 10, 15 and 16. [12]

Ecdysone agonists

The only commercial class of ecdysone agonists are the diacylhydrazines or 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 around 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 mammalian and environmental toxicity. Methoxyfenozide was given a presidential green chemistry award in 1998. Both tebufenozide and methoxyfenozide were registered by the United States Environmental Protection Agency (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. [13]

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 EPA, IGRs are also more compatible with pest management systems that use biological controls. [14] It was originally expected that insects would not be able to develop resistance to IGRs, [15] 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, [16]

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. The major use of insecticides is in agriculture, but they are also used in home and garden settings, industrial buildings, for vector control, and control of insect parasites of animals and humans.

<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">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">Chlorfenapyr</span> Chemical compound

Chlorfenapyr is an insecticde, and specifically a pro-insecticide. It is derived from a class of microbially produced compounds known as halogenated pyrroles.

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

Fenoxycarb is an 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.

<span class="mw-page-title-main">Benzoylurea insecticide</span> Class of insecticide

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:

In enzymology, a chitin synthase is an enzyme that catalyzes the chemical reaction

<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">Diamide insecticides</span> Class of insecticide

Diamide insecticides are a class of insecticides, active mainly against lepidoptera (caterpillars), which act on the insect ryanodine receptor. They are diamides of either phthalic acid or anthranilic acid, with various appropriate further substitutions.

<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.

<i>N</i>-Benzoyl-<i>N</i>-phenylurea Chemical compound

N-Benzoyl-N′-phenylurea (BPU) is the parent compound of the benzoylurea class of molecules, several of which are commercially useful insecticides. It consists of a urea core with a benzoyl amide on one nitrogen and a phenyl group on the other.

The Insecticide Resistance Action Committee (IRAC) was formed in 1984 and works as a specialist technical group of the industry association CropLife to be able to provide a coordinated industry response to prevent or delay the development of insecticide resistance in insect and mite pests. IRAC strives to facilitate communication and education on insecticide and traits resistance as well as to promote the development and facilitate the implementation of insecticide resistance management strategies.

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

Etoxazole is a narrow spectrum systemic acaricide used to combat spider mites. It targets a variety of mites in the egg, larvae and nymph stages however not the adult stage. It also exhibits insecticidal activity towards aphids, the green rice leafhopper and diamondback moth. The mode of action has been shown to inhibit chitin synthase (IRAC group 10B). Resistance due to its high efficacy and cross resistance when used with other acaricides are both of concern similar to was seen in the fast development of cross resistance in the previous generation of acaricides. The LC50 for resistant mite strains has been observed over 100,000 times greater than that of susceptible strains. Thus resistance management strategies are important in order to limit the increase of etoxazole resistant mite strains.

<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 synthase. 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">Chlorantraniliprole</span> Chemical compound

Chlorantraniliprole is an insecticide of the diamide class used for insects found on fruit and vegetable crops as well as ornamental plants.

<span class="mw-page-title-main">Diacylhydrazine insecticide</span> Class of insecticide

The diacylhydrazines, also known as bisacylhydrazines (BAHs) or dibenzoylhydrazines are appropriately substituted derivatives of dibenzoyl hydrazine. They do not immediately kill the insect, but produces premature unsuccessful moulting, which then causes the death of the insect. BAHs thus belong to the class of insect growth regulators.

<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.

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

Pymetrozine is an insecticide in the pyridine-azomethine chemical class, primarily utilized for controlling homopteran pests, such as aphids and whiteflies, in agricultural settings. Its mode of action selectively targets the feeding behavior of sap-feeding insects, causing them to cease feeding soon after ingestion. This unique mechanism limits its impact on non-target organisms, including beneficial insects. Pymetrozine has been extensively used on rice, potatoes, a wide variety of vegetable brassica crops and various other crops as an alternative to organophosphorus pesticides.

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. ↑ "The IRAC Mode of Action Classification Online". Insecticide Resistance Action Committee (IRAC). Retrieved 7 December 2024.
  13. ↑ 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 .
  14. ↑ Krysan, James; Dunley, John. "Insect Growth Regulators". Archived from the original on 30 November 2021. Retrieved 20 November 2010.
  15. ↑ 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.
  16. ↑ 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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