Insect be highly toxicity to the target sites,

Insect
Growth Regulator are the third generation of insecticide with a different type
compare to other insecticide depending on their mechanism through the influence
of insect development, disrupting the activities of endocrine system and
metamorphosis. The first generation was characterized by the chemical which
arise from a decades or centuries. The chemical includes oils and arsenics. The
second generation of insecticides was carbamates, organophosphates and
organochlorides. This insecticide was found during the synthesis programs with
the discovery of DDT. Others definition also referring with the process to the
bioactive compound by directed synthesis or involving the physiology and
ecology to produce an environmental friendly chemicals (Sparks & Hammock)

             IGRs also have a selective mechanism in their
mode of action with a major impact to inhibit the development of insect into
adults.Generally, the mechanism of IGR will delay the transformation and also
inhibit the cuticle formation in immature stage of insects (WHO, 2016).
However, in females, it also effecting the reproductive system by reducing the
number of egg laid and viability of eggs (Miura et al. 1976, Kelada et al.
1981). An IGR will be induced during the early stage of the insects and kill
the insect before the insects become adults and cannot reproduce any progeny. The
IGR is a form of “birth control” and can described as a control of insects
through the release of hormones/ IGR into the populations.There is not a
necessary for the IGR to be highly toxicity to the target sites, but may lead
to a changes and abnormalities against the insect survival (Siddal, 1976). There are
two compounds playing the roles in regulating the development of insects; (i)
ecdysone (called as moulting hormone MH), (ii) juvenile hormone (JH) which
directly interfered with the growth and development of the target insects.All
of these compounds interfere with insect metamorphosis, embryogenesis or
reproduction.

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            The IGR has been attempt for
mosquito control since 1974 against Aedes
larvae. Due to the low stability in the water, it was minimally used
against Culex and Anopheles species. The compound also not
induced rapid mortality in the treatment larvae. The compound will enter the
body through the cuticle or ingestion, unfortunately the larvae will not die
outright. The target larvae expose with a susceptibility problem during the
moulting periods. But recently, the new technology has been established and the
ingredient was converted into the matrix to control the formulation persistence
at a low concentration for a long time and thus controlling the larvae (Mulla, 1995).

IGRs
mechanism seem to be fit with a low risk to our environment, non-target
species, bird, fish and human. They have been used successfully without any
noticeable impact on other species and this trends will be acceptable to deploy
against mosquitoes and other vector program in the future. Newtypes of IGRs
will be continuously develop in the future, even the progression is quite slow,
but with the increasing number of epidemics caused by vector borne disease, it
become more faster than our expectation.

            Acetylcholinesterase is a hydrolase
vital for regulating neurotransmitter acetylcholine in mammals and insects, has
been used as a common target sitesfor insecticide
(Pang et al. 2012; Pang, 2006).
According to the similarity of target site between human and insects, it is
very important to develop a new insecticide with a different target site for
the pesticide. There are two types of insect growth regulators, which have a
different mode of actions, as follows: chitin synthesis inhibitors (cuticle
formation) and Juvenile hormone analogue