Pyridalyl insecticide

Pyridalyl insecticides have been globally developed and introduced in the market in Japan, Korea and Thailand with the trade name PLEO as of February 2006. Furthermore, registration approvals are expected in several countries, including United States, South Africa and Australia within the next 2-3 years. Developments are on-going in some EU, Latin American and Asian countries. 

H. Ikegami, K. Umeda, K. Tsushima, N. Matsuo, The discovery of pyridalyl a novel insecticidal agent for controlling lepidopterous pests, Pest Manage. Sci. 60 (1)... 

S. Isayama, S. Saito, K. Kuruda, K. Umeda, K. Kasamatsu, Pyridalyl, a novel insecticide potency and insecticidal selectivity, Arch. Insect Biochem. Physiol. 58 (4)... 

Pyridalyl is the only member of this class. It is a highly active insecticide against lepi-dopterous pests in cotton and vegetables. Its oral LD50 in rats is >5000 mg/kg. 

Characterization of cytotoxicity of pyridalyl, an insecticidal agent, to cultured insect and mammalian cells (T. Utsumi, Yamaguchi Univ., Japan)... 

PYridalyl Discovery, Insecticidal Activity, and Mode of Action im... 

We describe here the discovery of pyridalyl and its insecticidal activity, mode of action and information about commercial aspects. 

The discovery of a new insecticide begins with the generation of suitable lead compounds. They would be structurally modified to other compounds with higher insecticidal activity against target insects. Although various approaches may be used to create appropriate lead compounds, we should note that existing compounds were used as a lead compound in the case of pyridalyl. 

Pyridalyl Discovery, Insecticidal ActiviPy, and Mode of Action 1113 Cl... 

Table 30.3.4 Insecticidal activity of pyridalyl against insecticide resistant strain of P. xylostella.

In contrast to such strong insecticidal activity against lepidopterous insects, pyridalyl showed little insecticidal activity against species of Hemiptera, Coleop-tera and Orthoptera. Such selectivity of the compound is reasonably regarded as a preferable characteristic for uses in I PM programs, because some natural enemy insects are included in those families. In fact, pyridalyl showed minimal impacts on various beneficial arthropods such as parasitic wasps, predatory insects and mite and pollinators (Table 30.3.5) [1, 6, 7]. 

Pyridalyl Discovery, Insecticidal Activity, and Mode of Action 1117 Table 30.3.6 Labeled or proposed crops and use patterns (January, 2006). 

Thus, the symptoms and diagnoses in insects or cells described above suggests that pyridalyl has a different biochemical mode of action from any existing insecticides. The lack of cross-resistance between any existing insecticides also supports such a presumption. Studies to clarify the biochemical mode of the action are on-going. 

In Japan, not a few studies to establish local IPM programs using natural enemies have been carried out over the last several years. This is because administrations, as well as consumers, expect to reduce the usage of synthetic pesticides. From the grower s point of view, IPM programs might reduce their work in pesticide applications. Under such circumstances, the selective insecticidal activity of pyridalyl was of interest to researchers and has been incorporated into such studies, mainly since 2002. Spray programs were then introduced and accepted well in some areas. 

Thus, pyridalyl is expected to take an important role in IPMs and insecticide-resistance management programs and to contribute to agricultural production worldwide. 

Pyridalyl controls a wide variety of lepidopterous pest strains such as the diamondback moth (Plutella xylostella) which is resistant to various existing insecticides (8). This insecticide is also effective against thysanopterous pests. Moreover, it does not exert an adverse effect on various beneficial arthropods such as natural predator insects (e.g., Oristar-A ) and honeybees. Therefore, this novel insecticide is expected to be a usefiil material for controlling lepidopterous and thysanopterous pests in IPM and insecticide resistant management programs. 

This paper reviews the discovery, the structure-activity relationships, insecticidal activity and biological properties of pyridalyl. 

Based on overall considerations of insecticidal efficacy and safety to nontarget organisms (e.g. predatory insects, mammals, fish), S-1812 (pyridalyl) was finally selected as the most promising conq)ound for advanced precommercialization studies. 

Table 5. Insecticidal Activity of Pyridalyl against Lepidopterous Pests...

Extensive field trials have been carried out over several years on key target pests such as P, xylostella and H. virescens and pyridalyl has proven to be an outstanding insecticide. Pyridalyl shows very good efficacy for control of various lepidopterous and Ihysanopterous pests on cotton and vegetables without any phytotoxicity in practical treatment which range from 83 to 300g AI haC 8). 

Pyridalyl resulted from a major synthetic program based on a series of lead conq)ounds and has proven to be very active against the larvae of some inq>ortant pests of cotton and vegetable crops. Pyridalyl also controls insecticide-resistant strains of lepidopterous pests as well as susceptible strains. It produces unique insecticidal symptoms so t it may have a different mode of action from any other existing insecticides. Pyridalyl is safer to mammals and various beneficial arthropods so that it Avill provide an mq)ortant tool in IPM and insecticide resistant management programs. Pyridalyl will become a safer chemical, and certainly contribute to establishment of sustainable chemistry. 

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