PHENYLPYRAZOLES

Uses

The phenylpyrazoles form a new class of insecticides discovered in 1987. Currently only one member of the class, fipronil, has been commercialised. This class is considered to have a novel mode of action. Studies on fipronil have shown that it interferes with the passage of chloride ions through the y-aminobutyric acid (GABA) regulated chloride channel, thereby disrupting CNS activity. This is also the site of action of the cyclodiene insecticides, e.g. dieldrin and endosulfan.
There appears to be target site specificity between insects and mammals with fipronil displaying tighter binding (and thus higher potency) in the insect GABA chloride channel in comparison with that in vertebrates. Due to this mode of action, fipronil has proven highly effective in controlling insects that are resistant to other classes of insecticide.
Fipronil is effective at low dosage rates on many crop types and provides long-term protection against major lepidopterous and orthopterous pests on crops and against coleopterous larvae in soil. It is also used in public health and to control ectoparasites on pets and farm animals. It is the most recent chemical to be used for locust control and it has been widely used in a recent outbreak in Madagascar in 1997.