Insect growth regulator

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An insect growth regulator (IGR) is a substance (chemical) that inhibits the life cycle of an insect. IGRs are typically used as insecticides to control populations of harmful insect pests such as cockroaches and fleas. [1]

Contents

Advantages

Many IGRs are labeled "reduced risk" by the Environmental Protection Agency, meaning that they target juvenile harmful insect populations while causing less detrimental effects to beneficial insects. Many beekeepers have reported IGR's negatively affecting brood and young bees. Unlike classic insecticides, IGRs do not affect an insect's nervous system and are thus more friendly to "worker insects" within closed environments. [2] IGRs are also more compatible with pest management systems that use biological controls. In addition, while insects can become resistant to insecticides, they are less likely to become resistant to IGRs. [3]

Mechanism of action

As an insect grows it molts, growing a new exoskeleton under its old one and then shedding the old one to allow the new one to swell to a new size and harden. [3] IGRs prevent an insect from reaching maturity by interfering with the molting process. [4] This in turn curbs infestations because immature insects cannot reproduce. [1] Because these IGRs work by interfering with an insect's molting process, they kill insects more slowly than traditional insecticides. Death typically occurs within 3 to 10 days, depending on the IGR product, the insect's life stage at the time the product is applied, and how quickly the insect develops. Some IGRs cause insects to stop feeding long before they die. [4]

Hormonal IGRs

Hormonal IGRs typically work by mimicking or inhibiting the juvenile hormone (JH), one of the two major hormones involved in insect molting. IGRs can also inhibit the other hormone, ecdysone, large peaks of which trigger the insect to molt. If JH is present at the time of molting, the insect molts into a larger larval form; if absent, it molts into a pupa or adult. [4] IGRs that mimic JH can produce premature molting of young immature stages, disrupting larval development. [4] They can also act on eggs, causing sterility, disrupting behavior or disrupting diapause, the process that causes an insect to become dormant before winter. [3] IGRs that inhibit JH production can cause insects to prematurely molt into a nonfunctional adult. [3] IGRs that inhibit ecdysone can cause pupal mortality by interrupting the transformation of larval tissues into adult tissues during the pupal stage. [4]

Chitin synthesis inhibitors

Chitin synthesis inhibitors work by preventing the formation of chitin, a carbohydrate needed to form the insect's exoskeleton. With these inhibitors, an insect grows normally until it molts. The inhibitors prevent the new exoskeleton from forming properly, causing the insect to die. Death may be quick, or take up to several days depending on the insect. Chitin synthesis inhibitors can also kill eggs by disrupting normal embryonic development. [2] [3] Chitin synthesis inhibitors affect insects for longer periods of time than hormonal IGRs. These are also quicker acting but can affect predaceous insects, arthropods and even fish. [2] Compounds include benzoylurea pesticides.

Examples

Juvenoids

Juvenoids are juvenile hormone mimics, also known as juvenile hormone analogs:

Related Research Articles

Metamorphosis Profound change in body structure during the postembryonic development of an organism

Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some insects, fish, amphibians, mollusks, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, which is often accompanied by a change of nutrition source or behavior. Animals can be divided into species that undergo complete metamorphosis ("holometaboly"), incomplete metamorphosis ("hemimetaboly"), or no metamorphosis ("ametaboly").

Insecticide Pesticide used against insects

Insecticides are substances used to kill insects. 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 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.

Ecdysone Chemical compound

Ecdysone is a steroidal prohormone of the major insect molting hormone 20-hydroxyecdysone, which is secreted from the prothoracic glands. Insect molting hormones are generally called ecdysteroids. Ecdysteroids act as moulting hormones of arthropods but also occur in other related phyla where they can play different roles. In Drosophila melanogaster, an increase in ecdysone concentration induces the expression of genes coding for proteins that the larva requires, and it causes chromosome puffs to form in polytene chromosomes. Recent findings in the laboratory of Chris Q. Doe have found a novel role of this hormone in regulating temporal gene transitions within neural stem cells of the fruit fly.

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.

In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions. It is a physiological state with very specific initiating and inhibiting conditions. The mechanism is a means of surviving predictable, unfavorable environmental conditions, such as temperature extremes, drought, or reduced food availability. Diapause is observed in all the life stages of arthropods, especially insects. Embryonic diapause, a somewhat similar phenomenon, occurs in over 130 species of mammals, possibly even in humans, and in the embryos of many of the oviparous species of fish in the order Cyprinodontiformes.

Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago. Holometabolism is a synapomorphic trait of all insects in the superorder Endopterygota. Immature stages of holometabolous insects are very different from the mature stage. In some species the holometabolous life cycle prevents larvae from competing with adults because they inhabit different ecological niches. The morphology and behavior of each stage are adapted for different activities. For example, larval traits maximize feeding, growth, and development, while adult traits enable dispersal, mating, and egg laying. Some species of holometabolous insects protect and feed their offspring. Other insect developmental strategies include ametabolism and hemimetabolism.

Silverleaf whitefly Species of true bug

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Fungus gnat Group of insects

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Methoprene 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.

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.

Juvenile-hormone esterase

In enzymology, juvenile hormone esterase (JH esterase) is an enzyme that catalyzes the hydrolysis of juvenile hormone. For example, the juvenile hormone II (found in Lepidoptera):

Arthropod exoskeleton

Arthropods are covered with a tough, resilient integument or exoskeleton of chitin. Generally the exoskeleton will have thickened areas in which the chitin is reinforced or stiffened by materials such as minerals or hardened proteins. This happens in parts of the body where there is a need for rigidity or elasticity. Typically the mineral crystals, mainly calcium carbonate, are deposited among the chitin and protein molecules in a process called biomineralization. The crystals and fibres interpenetrate and reinforce each other, the minerals supplying the hardness and resistance to compression, while the chitin supplies the tensile strength. Biomineralization occurs mainly in crustaceans. In insects and arachnids, the main reinforcing materials are various proteins hardened by linking the fibres in processes called sclerotisation and the hardened proteins are called sclerotin. The dorsal tergum, ventral sternum, and the lateral pleura form the hardened plates or sclerites of a typical body segment.

<i>Chloridea virescens</i> Species of moth

Chloridea virescens, commonly known as the tobacco budworm, is a moth of the family Noctuidae found throughout the eastern and southwestern United States along with parts of Central America and South America.

Halloween genes Set of genes that influence embryonic development

The halloween genes are a set of genes identified in Drosophila melanogaster that influence embryonic development. All of the genes code for cytochrome P450 enzymes in the ecdysteroidogenic pathway (biosynthesis of ecdysone from cholesterol). Ecdysteroids such as 20-hydroxyecdysone and ecdysone influence many of the morphological, physiological, biochemical changes that occur during molting in insects.

Diflubenzuron 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.

Tebufenozide 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.

Hydroprene is an insect growth regulator used as an insecticide. It is used against cockroaches, beetles, and moths. Products using hydroprene include Gencor, Gentrol, and Raid Max Sterilizer Discs. Hydropene is a synthetic juvenile hormone mimic, disrupting insect larval development like molting.

Novaluron 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.

Flea treatments are procedures used to treat flea infestations in human or animal populations. They may treat both the itching caused by bites and may remove or kill the fleas themselves.

Buprofezin 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.

References

  1. 1 2 "Insect Growth Regulators" . Retrieved 20 November 2010.
  2. 1 2 3 Harris, Su; Waindle, Marianne. "Insect Growth Regulators (IGRs)" (PDF). Retrieved 20 November 2010.[ dead link ]
  3. 1 2 3 4 5 Krysan, James; Dunley, John. "Insect Growth Regulators" . Retrieved 20 November 2010.
  4. 1 2 3 4 5 "IGRs -- A Growing, But Misunderstood Group". GPN: Greenhouse Product News. Archived from the original on 2011-07-11. Retrieved 20 November 2010.
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