Diflubenzuron

Description

Diflubenzuron is an insecticide of the benzoylurea class.It is used in forest management and on field crops to selectively control insect pests, particularly forest tent caterpillar moths, boll weevils, gypsy moths, and other types of moths.It is a widely used larvicide in India for control of mosquito larvae by public health authorities. Diflubenzuron is approved by the WHO Pesticide Evaluation Scheme.

Description

Diflubenzuron is produced by the reaction of 2,6-difluorobenzamide with 4-chlorophenylisocyanate. Diflubenzuron was first registered as a pesticide in the United States in 1979. Environmental Protection Agency issued a Registration Standard for diflubenzuron in September 1985 (PB86-176500). In 1991, a Data Call-In was made to require additional residue chemistry and ecological effects data. The current Reregistration Eligibility Decision Document was issued in August 1997, reflecting analysis of the new data.

Description

Diflubenzuron is a benzoylphenylurea insecticide that inhibits chitin synthesis in insects with an IC₅₀ value of 0.611 nM for ¹⁴C-labeled N-acetyl-D-glucosamine incorporation in the cockroach. Specifically, it inhibits chitin synthetase at the egg and larval stages, leading to an inability to exit the egg or exocuticle, respectively. Diflubenzuron is genotoxic and mutagenic in mice at doses of 0.3, 1, and 3 mg/kg. Formulations containing diflubenzuron are used primarily in agricultural applications but are also used to control insects in livestock production.

Uses

Insecticide.

Uses

Diflubenzuron is a benzoylurea-based pesticide belonging to the benzamide class. Diflubenzuron is a chitin synthesis inhibitor. Diflubenzuron is used in both agriculture and forest management to selec tively control insect pests, particularly moths and weevils.

Uses

nsystemic insecticide used to control leaf-eating larvae and leaf miners in forestry, woody ornamentals and fruit trees.

Uses

Diflubenzuron is used for the control of a wide range of leaf-eating insects in forestry, woody ornamentals and fruit. It controls major pests on cotton, soyabean, citrus and tea and it also controls larvae of flies, mosquitoes and locusts. Diflubenzuron is also used as an ectoparasiticide.

Uses

An inhibitor of TCDD-induced CYP1a1 expression in HepG2 cells.

Definition

ChEBI: A benzoylurea insecticide that is urea in which a hydrogen attached to one of the nitrogens is replaced by a 4-chlorophenyl group, and a hydrogen attached to the other nitrogen is replaced bgy a 2,6-difluorobenzoyl group.

General Description

Colorless to yellow crystals. Used as a selective insecticide.

Air & Water Reactions

Hydrolyzed in alkaline solution above pH 9.0.

Reactivity Profile

A urea derivative.

Agricultural Uses

Insecticide, Larvicide: Diflubenzuron is used primarily on citrus, cattle feed, cotton, forestry, mushrooms, ornamentals, pastures, soybeans, standing water, sewage systems, and wide-area general outdoor treatment sites. The insecticide behaves as a chitin inhibitor to inhibit the growth of many leaf-eating larvae, mosquito larvae, aquatic midges, rust mite, boll weevil, and house-black-, and stable-flies. Diflubenzuron was first registered in the United States in 1979 for use as an insecticide.

Trade name

ADEPT®; ASTONEX®; DIMILIN®; DIMILIN® FLO; DIMILIN® WG-80; DU-112307®; DUPHAR® PH 60-40; ODC-45®; DIFLURON®; DU 112307®; LARGON®; LARVAKIL®; MICROMITE®; OMS 1804®; PDD 60401®; PH 60- 40®; PHILIPS-DUPHAR® PH 60-40; TH 60-40®; THOMPSON-HAYWARD® 6040; VIGILANTE®

Safety Profile

Moderately toxic by skin contact. Mildly toxic by ingestion. Mutation data reported. When heated to decomposition it emits very toxic fumes of Cl-, F-, and NOx.

Environmental Fate

Soil. The half-life in soil is <1 week (Hartley and Kidd, 1987). Di?ubenzuron degrades more rapidly in neutral or basic conditions but more slowly under acidic conditions (pH <6) (Ivie et al., 1980).
Chemical/Physical. Hydrolyzes in water to 4-chlorophenylurea (Verschueren, 1983).

Metabolic pathway

Diflubenzuron was the first active substance commercialised as a benzoylurea insect growth regulator and there is extensive published information on its degradation and metabolism. Detailed studies of the degradation in soils have shown that cleavage of the urea linkage is the major process. This also occurs in plants, insects and mammals but the formation of products in which diflubenzuron is hydroxylated in both rings is also an important metabolic process.

Degradation

Diflubenzuron was shown to be stable to hydrolysis in aqueous solution at acidic pH (DT₅₀> 56 days at pH 4) but was readily hydrolysed at pH 10 (DT₅₀ <3 days). In distilled water the DTa was 7 days (Ivie et al., 1980). The major degradation products isolated were 4-chlorophenylurea (2) and 2,6-difluorobenzoic acid (3). An additional minor product was 2,6- difluorobenzamide (4). The hydrolysis products are shown in Scheme 1. Additional products were formed under extreme conditions (121 °C under pressure).
Aqueous solutions of diflubenzuron are reported to be unstable to light but the solid is stable in sunlight (PM).

Toxicity evaluation

Diflubenzuron is an odorless, white, crystalline solid with a melting point of 230–232
C. It is almost insoluble in water (0.2 mg l1) and poorly soluble in apolar organic solvents.It is almost nonvolatile. It is relatively stable in acidic and neutral media but hydrolyses under alkaline conditions.
Diflubenzuron is difficult to be degraded in sterilized water under neutral or acidic conditions. However, it is degraded rapidly under field conditions. Application of diflubenzuron to water resulted rapid partition to sediment; the parent compound and 4-chlorophenylurea (CPU) may persist on sediment for more than 30 days.
The rate of degradation of diflubenzuron in soil is strongly dependent on the particle size. For larger particles (10 microns), the half-life is 8–16 weeks and for smaller particles (2 microns), it is 0.5–1 week. Almost all of the parent compound breaks down to form 2,6-difluorobenzoic acid (DFBA) and CPU. A very minor amount forms 4-chloroaniline (PCA) which rapidly binds to the soil. Under field conditions, diflubenzuron has very low mobility.
Very little diflubenzuron is absorbed, metabolized, or translocated in plants. It also is not readily taken up from treated soil.
Diflubenzuron has very low vapor pressure (<2×10^-7 Pa at 25°C) and its atmospheric half-life is only several hours. Therefore, it is not expected that diflubenzuron will be present in air for extended periods and the long-range transport and redeposition of diflubenzuron is expected to be negligible.