benomyl (Benlate) Chemical Profile 8/89
CHEMICAL NAME: Methyl 1-(butylcarbamoyl)-2-benzimidazole carbamate
TRADE NAME(S): Benlate, Tersan-1991 (56)
FORMULATION(S): Wettable powder 50%; Benlate OD 50% oil
TYPE: Carbamate fungicide
BASIC PRODUCER(S): E.I. duPont de Nemours and Co., Inc.
1007 Market St.
Wilmington, DE 19898
STATUS: General use. RPAR; criteria possibly met or
exceeded: reduction in nontarget species (rebutted), mutagenicity,
teratogenicity, reproductive effects, hazard to wildlife. PD 1
published 12/6/77. PD 2/3 completed and Notice of Determination
published 8/30/79; comment period closed 9/28/79. PD 4 completed and
Notice of Determination published 10/20/82. The Notice requires use
of either cloth or commercially available disposable dust masks by
mixer/loaders of benomyl intended for aerial application and that
registrants of benomyl products conduct field monitoring studies to
identify residues that may enter aquatic sites after use on rice (22).
PRINCIPAL USES: Foliar systemic against wide range of diseases on
fruits, nuts, vegetables, field crops, turf and ornamentals. Also
used against Dutch elm disease. Both a preventative and eradicant
The DuPont Company has voluntarily withdrawn all postharvest uses of
benomyl (Benlate) Fungicide in the United States. Crops affected
include apples, pears, pineapples, citrus, and all stone fruits.
The withdrawl from postharvest application is effective as of 8/15/89.
Resistance in some fungus strains has been noted (48).
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C14 H18 N4 O3 (26)
MOLECULAR WEIGHT: 290.3 (26)
PHYSICAL STATE: Colorless crystalline solid (pure compound) (26)
ODOR: Faint acrid odor (pure compound) (26)
MELTING POINT: Decomposes before melting (pure compound) (26)
SOLUBILITY: 3.8 mg/l water at pH 7 and 20 C (pure compound)
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: NA
NIOSH RECOMMENDED LIMIT: NA
ACGIH RECOMMENDED LIMIT: TWA (Time Weighted Average) = 0.8 ppm, 10
mg/m3; STEL (Short Term Exposure Limit) = 1.3
ppm, 15 mg/m3 (15a).
A. ACUTE TOXICITY
DERMAL: It is mildly irritating to the skin but without
dermatitis hazard (26).
LD50 = >10,000 mg/kg (rabbit) (31d)
ORAL: LD50 = >10,000 mg/kg (rat) (6)
INHALATION: LC50 = >2 mg/l (dry product, 4-hour exposure,
EYES: 10 mg of dry 50% powder or 0.1 ml of 10%
suspension in mineral oil caused only temporary mild conjunctival
irritation (rabbit (31d).
B. SUB-CHRONIC AND CHRONIC TOXICITY:
In 90-day feeding trials there was no evidence of toxicity for
rats receiving 2500 mg/kg diet. In 2-year feeding trials with rats and
dogs a low order of toxicity occurred (26).
In two-year feeding studies (with 2500 ppm the highest dietary
level), the no-observable effect level was 2500 ppm for rats and 500
ppm for dogs. In dogs fed 2500 ppm, there was biochemical evidence of
impaired liver function and histological evidence of liver cirrhosis.
No oncogenic effects were observed in either rats or dogs (31d).
Rat reproduction, 3-generation: No adverse effect on reproduction
performance at dietary levels as high as 2500 ppm; no pathological
changes found in tissues from weanling pups of F3B generation (2500
Teratogenicity (rat, rabbit): Not embryotoxic or teratogenic to rats
by dietary administration at levels as high as 5000 ppm (equivalent to
373 mg/kg/day, approx.). By gavage, statistically significant
teratogenic response was obtained at dose levels of 62.5 mg/kg/day and
above, but not at 30 mg/kg/day and below. No teratogenic effects were
found in studies with rabbits fed 500 ppm in the diet (equivalent to 20
mg/kg/day, approx.) (31d).
Mutagenicity: Negative results were obtained in the following assays:
1. Host mediated assay
2. CHO point mutation
3. Reverse-mutation tests
4. Rat dominant lethal at 2500 ppm in diet
5. Drosophila test for measuring recessive lethal damage
6. DNA repair (UDS)
Weak activity has been reported by various investigators in some S.
typhimurium strains. However, other Ames tests were negative. Some
cytogenetic effects have been reported; such effects may be explained
by the spindle effects of benomyl (31d).
IV. ENVIRONMENTAL CONSIDERATIONS
Hazardous to fish. Relatively nonhazardous to honey bees.
Nonphytotoxic when used as directed (48).
The LC50 for mallard ducks and quail was >5000 mg/kg (26).
Bluegill sunfish LC50 (96-hour exposure) is 2.6 ppm
Catfish LC50 (96-hour exposure) is 0.071 ppm
Goldfish LC50 (96-hour exposure) is 4.2 ppm
Rainbow trout LC50 (96-hour exposure) is 0.41 ppm (31d).
Benomyl degrades slowly in the soil. The half-life of the total
benzimidazole-containing residues is about 3 to 6 months on turf,
representing a vegetative situation, and about 6 to 12 months on bare
soil - J. Ag. Food Chem. 22(3) 413 (1974). Very little leaching or
runoff occurs with benomyl even under rigorous exposure conditions
V. EMERGENCY AND FIRST AID PROCEDURES
The chemical information provided below has been condensed
from original source documents, primarily from "Recognition and
Management of Pesticide Poisonings", 3rd ed. by Donald P. Morgan,
which have been footnoted. This information has been provided in
this form for your convenience and general guidance only. In
specific cases, further consultation and reference may be required
and is recommended. This information is not intended as a sub-
stitute for a more exhaustive review of the literature nor for the
judgement of a physician or other trained professional.
If poisoning is suspected, do not wait for symptoms to develop.
Contact a physician, the nearest hospital, or the nearest Poison
KNOWN OR SUSPECTED ADVERSE EFFECTS: Mild irritant. Does not
inhibit cholinesterase enzyme (25).
SKIN CONTACT: Wash contaminated skin with soap and water (25).
INGESTION: Ingestions of small amounts (less than 10 mg/kg
body weight) occurring less than an hour before treatment, are probably
best treated by: Syrup of Ipecac, followed by 1-2 glasses of water.
Dose for adults and children over 12 years: 30 ml. Dose for children
under 12 years: 15 ml (25).
EYE CONTACT: Flush contaminated eyes with copious amounts of
fresh water for 15 minutes (25).
NOTES TO PHYSICIAN:
INGESTIONS of LARGE amounts (more than 10 mg/kg) occurring less than an
hour before treatment, should probably be treated by gastric lavage:
A. INTUBATE stomach and ASPIRATE contents.
B. LAVAGE stomach with slurry of ACTIVATED CHARCOAL in 0.9% saline.
Leave 30-50 gm activated charcoal in the stomach before
C. SODIUM SULFATE, 0.25 gm/kg in tap water, as a cathartic.
CAUTION: Hydrocarbons (kerosene, petroleum distillates) are
included in some formulations of these chemicals.
Ingestions of very LARGE AMOUNTS may cause CNS
depression. In this case, IPECAC IS CONTRAINDICATED.
Also, gastric intubation incurs a risk of HYDROCARBON
PNEUMONITIS. For this reason observe the following
(1) If the victim is unconscious or obtunded and
facilities are at hand, insert an ENDOTRACHEAL TUBE
(cuffed, if available) prior to gastric intubation.
(2) Keep victim's HEAD BELOW LEVEL OF STOMACH during
intubation and lavage (Trendelenburg, or left
lateral decubitus, with head of table tipped
downward). Keep victim's head turned to the left.
(3) ASPIRATE PHARYNX as regularly as possible to remove
gagged or vomited stomach contents.
INGESTIONS occurring MORE THAN an HOUR before treatment are probably
best treated only by ACTIVATED CHARCOAL, 30-50 gm, and SODIUM or
MAGNESIUM SULFATE, 0.25 gm/kg, as described above.
There are no specific antidotes for these chemicals. Because
manifestations of toxicity do occasionally occur in peculiarly
predisposed individuals, MAINTAIN CONTACT with victim for at least 72
hours so that unexpected adverse effects can be treated promptly (25).
VI. FIRE AND EXPLOSION INFORMATION
GENERAL: Auto ignition temperature: 220 C. May be ignited by heat or
open flame. Fine dust dispersed in air (particularly in confined
spaces) may ignite if exposed to high temperature ignition source. Use
only with adequate ventilation.
Fire fighting: If area is heavily exposed to fire and if conditions
permit, let fire burn itself out since water may increase the area
contaminated. Wear self-contained breathing apparatus and appropriate
protective equipment for fire fighting and cleanup.
Hazardous decomposition product: n-butylisocyanate, a strong
EXTINGUISHER TYPE: Use multi-purpose dry powder or water spray. Cool
exposed containers with water (31e).
Compatible with other alkaline pesticides (48).
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Keep out of reach of children. Keep away from
fire and sparks. Never allow products containing benomyl to become wet
during storage. This may lead to certain chemical changes which will
reduce the effectiveness of these formulations as fungicides. Keep
container tightly closed when not in use. Do not contaminate water,
food, or feeds by storage. Do not reuse container (31d).
PROTECTIVE CLOTHING: Where dust levels may exceed AEL value, an
approved pesticide respirator, goggles, and protective clothing should
be worn (31e).
IX. PROCEDURES FOR SPILLS AND LEAKS
IN CASE OF EMERGENCY, CALL, DAY OR NIGHT
PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
Clean up promptly by scoop or vacuum; flush remaining residue with
water (prevent contamination of sewers or bodies of water). Where dust
levels may exceed AEL value, an approved pesticide respirator, goggles,
and protective clothing should be worn (31e).
X. LITERATURE CITED
6. Farm Chemicals Handbook, 66th ed. 1980. G. L. Berg, C. Sine,
S. Meister, and H. Shephard, eds. Meister Publ. Co.,
15a. American Conference of Governmental Industrial Hygienists. 1983.
TLVs: threshold limit values for chemical substances and
physical agents in the work environment with intended changes
for 1983-84. Cincinnati, OH. 93 pp.
22. U.S. Environmental Protection Agency, Office of Pesticide
Programs. 1983. June 1983 status report on rebuttable
presumption against registration (RPAR) or special review
process, registration standards and the data call in
programs. Washington, DC. 45 pp.
25. Morgan, D.P. 1982. Recognition and management of
pesticide poisonings, 3rd ed. U. S. Environmental Protection
Agency, Washington, DC. 120 pp.
26. The Pesticide Manual: A World Compendium, 6th ed. 1979. C. R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 655 pp.
31d. E. I. du Pont de Nemours and Co., Inc., Biochemicals Department.
1983. Technical data sheet: benomyl. Wilmington, DE.
31e. E. I. du Pont de Nemours and Co., Inc., Biochemicals Department.
1982. Material safety data sheet for Benlate fungicide.
48. Harding, W.C. 1979-80. Pesticide profiles, part two: fungicides
and nematicides. Univ. Maryland, Coop. Ext. Service Bull.
283, 22 pp.
56. Farm Chemicals Handbook, 70th ed. 1984. R. T. Meister, G. L.
Berg, C. Sine, S. Meister, and J. Poplyk, eds. Meister
Publishing Co., Willoughby, OH.