Pyridalyl activity

New agrochemicals introduced in the past five years include new chemistries with known modes of action, such as the protoporphyrinogen inhibitor bencarba-zone, the phytoene desaturase picolinafen and beflutamid, and sodium channel pyrethroids new chemistries with possibly new modes of action, such as flonic-amid and pyridalyl and new chemistries with established new modes of actions, such as flubendiamide, which activates ryanodine-sensitive intracellular calcium release channels, ryanodine receptors RyR, in insects. 

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. 

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. 

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). 

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. 

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

LC50 values of pyridalyl against various lepidopterous larvae were between 0.77 and 4.48 ppm as shown in Table 5. Pyridalyl also showed good activity against thysanopterous insects at 100 ppm (data are not shown). The con oimd... 

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

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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