Insecticides > Pyrazole insecticides
Acaricides / Miticides > Pyrazole acaricides
Fipronil is a broad-spectrum insecticide active by contact and ingestion, which is effective against adult and larval stages. It disrupts the insect central nervous system by interfering with the gamma-aminobutyric acid (GABA) - regulated chlorine channel. It is systemic in plants and can be applied in a variety of ways. Fipronil can be used at the time of planting to control soil pests. It can be applied in-furrow or as a narrow band. It requires thorough incorporation into the soil. Granular formulations of the product can be used in broadcast applications to paddy rice. As a foliar treatment, fipronil has both preventative and curative activity. The product is also suitable for use as a seed treatment.
Vil-Nil is a compost-incorporated granule formulation for the control of vine weevils in ornamental plants. This formulation binds to plant roots and acts as a preventative treatment. It persists in the soil for at least two seasons. Fipronil has also been developed for use in baits for the control of grasshoppers, cockroaches and ants.
In field trials, fipronil showed no phytotoxicity at the recommended rates. It controls organophosphate-, carbamate- and pyrethroid-resistant species and is suitable for use in IPM systems. Fipronil does not adversely interact with ALS-inhibiting herbicides.
Bayer CropScience voluntarily withdrew registrations of certain pesticide products that contain fipronil for use on rice or rice seed. The cancellation was effective from the 1st of July 2004.
Two reports in J. Econ. Entomol. (2003) summarise the toxicity of fipronil against the Formosan subterranean termite, Coptotermes formosanus Shiraki, which is an economically important pest in the US. Acute toxicity from topical applications was greater in workers than soldiers. Later assessments showed little difference on the two groups, with an LD50 at 72h of < 2.0 ng/insect. Treated soldiers placed near untreated workers resulted in higher mortality of the workers, but the reverse process (from treated workers to untreated soldiers) did not result in significant horizontal transmission. Fipronil rates of up to 0.063% showed no repellency, whereas the higher rate of 0.125% was repellent to workers.
alfalfa, aubergines, bananas, beans, brassicas, cabbages, cauliflowers, chillies, crucifers, cucurbits, citrus, coffee, cotton, crucifers, garlic, maize, mangos, mangosteens, melons, oilseed rape, onions, ornamentals, peas, peanuts, potatoes, rangeland, rice, soybeans, sugar beet, sugar cane, sunflowers, sweet potatoes, tobacco, tomatoes, turf, watermelons
Maize: 200 g ai/ha; 2, 500 g ai/tonne seed
Sugar beet: 200 g ai/ha
Sunflowers: 200 g ai/ha; 5, 000 g ai/tonne seed
Molecular weight:437.2; Physical form:White solid. Density:1.477-1.626 (20 °C); Melting point:200-201 °C; ( tech., 195.5-203 °C); Vapour pressure:3.7 ×10-4 mPa (25 °C); Henry constant:3.7 ×10-5 Pa m3 mol-1 ( calc.); Partition coefficient(n-octanol and water):logP = 4.0 (shake flask method); Solubility:In water 1.9 ( pH 5), 2.4 ( pH 9), 1.9 (distilled) (all in mg/l, 20 °C). In acetone 545.9, dichloromethane 22.3, hexane 0.028, toluene 3.0 (all in g/l, 20 °C).; Stability:Stable in water at pH 5 and 7; slowly hydrolysed at pH 9 ( DT50 c. 28 d). Stable to heat. Slowly degrades in sunlight (c. 3% loss after 12 d continuous irradiation); rapidly pho;
Oral:Acute oral LD50 for rats 97, mice 95 mg/ kg. Percutaneous:Acute percutaneous LD50 for rats >2000, rabbits 354 mg/kg. Not a skin or eye irritant ( OECD criteria). Not a skin sensitiser. Inhalation: LC50 (4 h) for rats 0.682 mg/l ( tech.; nose only exposure).
Algae: EC50 (96 h) for Scenedesmus subspicatus 0.068 mg/l; (120 h) for Selenastrum capricornutum >0.16, Anabaena flos-aquae>0.17 mg/l.Bees:Highly toxic to honeybees, both by direct contact and by ingestion. However, no risk to bees when used as a soil or seed treatment.Birds:Acute oral LD50 for bobwhite quail 11.3, mallard ducks >2000, pheasants 31, red-legged partridges 34, house sparrows 1120, pigeons >2000 mg/kg. Dietary LC50 (5 d) for bobwhite quail Daphnia: LC50 (48 h) 0.19 mg/l; for D. carinata(48 h) 3.8 mg/l.Fish:Acute LC50 (96 h) for bluegill sunfish 85, rainbow trout 248, European carp 430 mg/l.Worms:Non-toxic.
Fate in soil:
In laboratory studies, fipronil has a half-life of 122-128 days in oxygenated sandy loam soil. In field studies, half-life on soil surfaces ranges from 0.7 to 1.7 months, whilst for soil incorporation it is 3 to 7.3 months. Fipronil has low soil mobility; it binds to the soil and the residues remain in the upper 12 inches of soil. The average Koc value is 803. There is little potential for groundwater contamination.
Aerobic soil metabolism studies give the half-life of fipronil in sandy loam to be 122 days.
In anaerobic systems, fipronil degrades slowly in water and sediment with a half-life of 116-130 days. In an aerobic metabolism study, fipronil readily partitioned from the aqueous layer into the sediment.
In a field dissipation study in Niger, 25% of the original applied dose of fipronil (8 g ai/ha) was recovered after 3 days. Four degradates were also identified including a sulfide due to reduction in soil, an amide from hydrolysis, and a sulfone from oxidation in soil. A desulfinyl photodegradate was also identified.
Thus in soil, fipronil dissipates by soil binding along with gradual microbial breakdown.
Fate in aquatic systems:
Fipronil is stable to hydrolysis at 22°C at pH 9.1 (DT50 1100 days) and pH 7.1 (DT50 1100 days), whereas at 32°C, the half-life is 11.3 days at pH 9.1 and 15.6 days at pH 7.1.
Fipronil undergoes photodegradation in water with a half-life of 3.6 hours. Thus photolysis is a more important pathway for degradation of aqueous fipronil.
Ground water concentrations of fipronil calculated using the SCI-GRO model (shallow groundwater on highly vulnerable US sites) were 0.055 ppb for maize and 0.00804 ppb for rice. Based on environmental fate assessment, fipronil has the potential to move into surface waters. However, when fipronil is used as an in-furrow application, the run-off potential of fipronil residues is expected to be lower than for unincorporated surface application techniques. The maximum fipronil surface water concentrations for acute and chronic exposure based on GENEEC surface water modelling were found to be for corn, acute 2.05 ppb, chronic 0.78 ppb; for rice, acute 1.45 ppb, chronic 0.40 ppb. These values are less than the drinking water lowest levels of concern of 810 ppb and 220 ppb in surface and ground water for acute risk, and 6.67 ppb and 1.77 ppb for chronic risk.
Signal Word:WARNING; Hazard Class:II(Moderately hazardous)
95%Tech, 80%WDG, 200 g/l SC
Oral Acute oral LD50 for rats 97, mice 95 mg/kg.
Skin and eye Acute percutaneous LD50 for rats >2000, rabbits 354 mg/kg. Not a skin or eye irritant (OECD criteria). Not a skin sensitiser.
Inhalation LC50 (4 h) for rats 0.682 mg/l (tech.; nose only exposure).
NOEL (2 y) for rats 0.5 mg/kg diet; (18 mo) for mice 0.5 mg/kg diet; (52 w) for dogs 0.2 mg/kg b.w. daily (combined sexes).
ADI (JMPR) 0.0002 mg/kg b.w. ; group ADI for fipronil and fipronil desulfinyl.
Other Non-mutagenic, non-teratogenic; no adverse effect on reproductive performance. Clinical signs of toxicity consistent with the interaction of the molecule at a neurotransmitter receptor were observed in all species tested, but were completely reversible.
Toxicity class WHO (a.i.) II
Mode of action Broad-spectrum insecticide, toxic by contact and ingestion. Moderately systemic and, in some crops, can be used to control insects when applied as a soil or seed treatment. Good to excellent residual control following foliar application. Uses Control of multiple species of thrips on a broad range of crops by foliar, soil or seed treatment. Control of corn rootworm, wireworms and termites by soil treatment in maize. Control of boll weevil and plant bugs on cotton, diamond-back moth on crucifers, Colorado potato beetle on potatoes by foliar application. Control of stem borers, leaf miners, planthoppers, leaf folder/rollers and weevils in rice. Foliar application rates range from 10-80 g/ha; soil treatment rates 100-200 g/ha.