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The information in this profile may be out-of-date. It was last revised in 1996. EXTOXNET no longer updates this information, but it may be useful as a reference or resource.

Please visit the National Pesticide Information Center (NPIC) to find updated pesticide fact sheets. If you don't find a fact sheet related to your question, feel free to call 1-800-858-7378. NPIC is open five days a week from 8:00am to 12:00pm Pacific Time.

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E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Oregon State University, the University of Idaho, and the University of California at Davis and the Institute for Environmental Toxicology, Michigan State University. Major support and funding was provided by the USDA/Extension Service/National Agricultural Pesticide Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Diflubenzuron

Trade and Other Names: Diflubenzuron is sold under the trade name Dimilin. Other trade names inlcude DU112307, ENT-29054, Micromite, and OMS-1804.

Regulatory Status: Some formulations of diflubenzuron may be classified as Restricted Use Pesticides (RUPs) in the U.S. RUPs may be purchased and used only by certified applicators. Diflubenzuron is classified as toxicity class III - slightly toxic. Products containing it bear the Signal Word CAUTION.

Chemical Class: benzoylphenylurea

Introduction: Diflubenzuron is a benzoylphenyl urea used on forest and field crops to selectively control insects and parasites. Principal target insect species are the gypsy moth, forest tent caterpiller, several evergreen eating moths, and the boll weevil. It is also used as a larvae control chemical in mushroom operations and animal houses. Diflubenzuron is a stomach and contact poison. It acts by inhibiting the production of chitin, a compound that makes the outer covering of the insect hard and thus interferes with the formation of the insect's cuticle or shell. It is available as a suspension concentrate, wettable powder, or in granules.

Formulation: It is available as a suspension concentrate, wettable powder, or in granules.

Toxicological Effects:

• Acute toxicity: No overt signs of toxicity were observed in any of the acute studies conducted [16]. The oral LD50 in rats and mice is greater than 4640 mg/kg, and the dermal LD50 is greater than 10,000 mg/kg in rats and greater than 4000 mg/kg in rabbits. It is nonirritating to skin and slightly irritating to eyes [8].
• Chronic toxicity: Rats given moderate amounts of the compound for 2 years had enlarged spleens, while mice in a similar study had liver and spleen enlargement at slightly lower levels of exposure. In a study with cats fed over a wide range of doses for 21 days, all of the females had dose related blood chemistry changes at low doses and the males exhibited changes at dose levels that were slightly higher [9]. The changes were reversible. The chemistry changes were associated with the formation of methemoglobin, a form of hemoglobin that is unable to carry oxygen.
• Reproductive effects: Day-old ducks and turkeys fed moderate amounts of the pesticide in their diets for 90 days had decreased testosterone levels after 42 days, but this did not occur in chickens and pheasants in the same study. Combs and wattles, which reflect hormone activity, showed some abnormalities. Some were underdeveloped and others more developed compared to controls. A short-term decrease in testosterone levels was shown in the sexually immature rats but no clear cut change was shown in young bull calves [16]. A three-generation study on rats at low doses showed no effect on mating performance. It does not appear that diflubenzuron has a significant effect on reproduction [16,28].
• Teratogenic effects: Diflubenzuron does not appear to be teratogenic. Newborn rats and rabbits did not develop any birth defects after their mothers were exposed to low levels of diflubenzuron (1 to 4 mg/kg/day) on days 6 to 18 of gestation [16,28].
• Mutagenic effects: Extensive testing on mamalian cells and on bacterial cells shows that diflubenzuron is not mutagenic [16,28].
• Carcinogenic effects: Rats fed diets containing low to moderate amounts of diflubenzuron daily for 2 years had no increase in the number of new or abnormal tissue growths or lesions. Mice fed low doses for 80 weeks showed no significant tumor development. Other studies on both species at higher levels were also negative for malignant tumors [16]. Diflubenzuron does not appear to be carcinogenic.
• Organ toxicity: Animal studies have shown the liver and spleen to be target organs.

• Fate in humans and animals: Intestinal absorption in mammals decreases with increasing dose levels [28]. For example, in rats , the total excretion in urine and bile decreased from about 50% of the dose at 4 mg/kg to only 4% at 900 mg/kg. Mice showed similar results. A cow given 10 mg/kg orally, eliminated almost all of the product over a 4-day period. There were only minute amounts of the pesticide in the milk. The chemical is not degraded in the digestive tract, but that which is absorbed by the gut is completely broken down before excretion [16]. Rabbits' skin absorbed only very small amounts, all of which was recovered in the urine. Chickens excreted almost all of an oral dose in 13 days. Their eggs had low levels of pesticide residues (0.3 to 0.6 mg/kg) from day 9 to the end of the 9-week study. Body tissues (non-fatty) do not retain diflubenzuron [16].

Ecological Effects:

• Effects on birds: Diflubenzuron is practically nontoxic to wild birds. Bobwhite quail and mallard ducks both have an 8-day dietary LC50 of greater than 4640 ppm [4,7,8].
• Effects on aquatic organisms: Diflubenzuron is practically nontoxic to fish and aquatic invertebrates. The LC50 values (96-hour) for diflubenzuron in various fish are: bluegill sunfish, 660 mg/L; rainbow trout, 240 mg/L; saltwater minnow, 255 mg/L; and channel catfish, 180 mg/L. In oyster larvae and juveniles EC50 values were 130 and 250 mg/L, respectively [4,7,8]. Arthropods are most susceptible in the premolting stage. For instance, fiddler crabs, exposed for as little as 1 week at levels up to 0.05 mg/L exhibited limb regeneration effects [29]. Fish tissue can show some traces of the metabolites when water is contaminated with diflubenzuron; however, tissue concentrations decline steadily with time in clean water.
• Effects on other organisms: The compound is nontoxic to bees [4].

Environmental Fate:

• Breakdown in soil and groundwater: Diflubenzuron has a low persistence in soil. The rate of degradation in soil is strongly dependent on the particle size of the diflubenzuron [12]. It is rapidly degraded by microbial processes. The half-life in soil is 3 to 4 days [19]. Under field conditions, diflubenzuron has very low mobility [8,19].
• Breakdown in water: In sterilized water (no microbes), there appears to be little degradation under neutral or acidic conditions. However, under field conditions, it is degraded rapidly. Residues could not be detected in field water 72 hours after an application of 110 g/hectare. Other studies suggest a half-life of 1 to 3 weeks [4,7,8].
• Breakdown in vegetation: Very little diflubenzuron is absorbed, metabolized, or translocated in plants. Residues on crops such as apples have a half-life of 5 to 10 weeks. The half-life in oak leaf litter is 6 to 9 months [4,7,8].

Physical Properties:

• Appearance: Diflubenzuron is a white crystalline solid [7].
• Chemical Name: 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea [7]
• CAS Number: 35367-38-5
• Molecular Weight: 310.70
• Water Solubility: 0.14 mg/L @ 20 C, insoluble [7]
• Solubility in Other Solvents: DMSO s.; acetone s.s.; methanol s.
• Melting Point: 210-230 C (technical with decomposition) [7]
• Vapor Pressure: <0.033 mPa @ 50 C [7]
• Partition Coefficient: Not Available
• Adsorption Coefficient: 10,000 [19]

Exposure Guidelines:

• ADI: 0.02 mg/kg/day [30]
• MCL: Not Available
• RfD: 0.02 mg/kg/day [31]
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Uniroyal Chemical Co., Inc.
Benson Road
Middlebury, CT 06749

• Phone: 203-573-2000
• Emergency: 203-723-3670
  

References:

References for the information in this PIP can be found in Reference List Number 9

DISCLAIMER: The information in this profile does not in any way replace or supersede the information on the pesticide product labeling or other regulatory requirements. Please refer to the pesticide product labeling.