paclobutrazol (Clipper 50 WP) Herbicide Profile 8/85
CHEMICAL FACT SHEET FOR:
FACT SHEET NUMBER: 62
DATE ISSUED: AUGUST 14, 1985
1. DESCRIPTION OF CHEMICAL
- Generic Name: (+/-)-(R*,R*)-B-[(4-chlorophenyl)methyl]-alpha-
- Common Name: paclobutrazol
- Code Name: PP333
- Trade Name: Clipper 50 WP
- EPA Shaughnessy Code: 125601
- Chemical Abstracts Service (CAS) Registry Number: 76738-62-0
- Year of Initial Registration: 1985
- Pesticide Type: Plant growth regulator
- Chemical Family:
- U.S. Foreign Producers: ICI Americas Inc.
2. USE PATTERNS AND FORMULATIONS
- Application sites: Ornamental trees (deciduous and broadleaf
- Types of formulations: Wettable powder (50% a.i.)
- Types and methods of application: Applied in a pressurized tree
- Application rates: Rates vary depending upon tree size; dosage for
smallest treatable tree is 0.006 oz. active ingredient per tree.
- Usual carriers: Water
3. SCIENCE FINDINGS
- Physical state: solid
- Color: white
- Odor: not significant
- Melting point: 165-166 degrees C
- Density: 1.22g/cubic cm
- Vapor pressure: 1.5 x 10(-4) Pa at 50 degrees C
8 x 10(-6) Pa at 30 degrees C
1 x 10(-6) Pa at 20 degrees C (by extrapolation)
- Water 35 ppm
- Cyclohexanone 18%
- Methanol 15%
- Acetone 11%
- Methylene dichloride 10%
- Xylene 6%
- Propylene glycol 5%
- Hexane <1%
Octanol/water partition coefficient: Log P 3.2
- Unusual handling characteristics: None
- Acute toxicology results
- Acute oral toxicity (rat): 1.95 g/kg (male), 1.33 g/kg (female),
Toxicity Category III
- Acute dermal toxicity (rat): Greater than 2 g/kg, Toxicity
- Primary skin irritation (rabbit): Paclobutrazol caused mild skin
irritation. Toxicity Category III
- Primary eye irritation (rabbit): Paclobutrazol caused reversible
corneal opacities with irritation lasting 72 hours. Toxicity
- Dermal sensitization (guinea pig): Paclobutrazol is not a skin
- Acute inhalation toxicity (rat): Greater than 766 mg/cu. m
(male), 359-766 mg/cu. m (female), Toxicity Category II
- Chronic toxicology results:
- 21-day dermal (rabbit): NOEL is 10 mg/kg/day, LEL is 100 mg/kg/
- 90-day feeding (rat): NOEL is 250 ppm, LEL is 1,250 ppm
- One year feeding (dog): NOEL is 15 mg/kg/day, LEL is 75 mg/kg/day
- Teratology (rat): NOEL (maternal toxicity) is greater than 100
mg/kg/day (highest dose tested). NOEL (fetal effects) is 10
- Teratology (rabbit): Within limitations of study (low fertility),
NOEL (maternal toxicity) is 25 mg/kg/day. LEL is 75 mg/kg/day.
- Mutagenicity: Paclobutrazol does not cause mutagenic effects.
- Metabolism: Results from rat and dog studies indicate that
paclobutrazol and its metabolites are rapidly eliminated.
- Major routes of exposure: Mixers, loaders, and applicators would
receive the most exposure via skin/eye contact and inhalation.
Physiological and Biochemical Behavioral Characteristics
- Mechanism of pesticidal action: Paclobutrazol acts as a plant
growth regulator and reduces regrowth in ornamental trees following
- Adsorption and leaching in basic soil types: Paclobutrazol could
leach in sandy soils with low organic content. In other soil types,
the chemical does not have a high propensity to leach.
- Loss from photodegradation: Paclobutrazol does not photodegrade
after exposed to 10 days of simulated sunlight.
- Resultant average persistence: Paclobutrazol degrades aerobically
in soil with half-lives of about 1-7 months depending upon soil
type. Paclobutrazol is not expected to hydrolyze in the environment.
- Avian acute oral toxicity (Mallard): greater than 7,913 mg/kg
- Avian dietary toxicity (Bobwhite quail): greater than 5,000 ppm
- Avian dietary toxicity (Mallard): greater than 20,000 ppm
- Fish acute toxicity (Bluegill): 23.6 mg/l
- Fish acute toxicity (Rainbow trout): 27.B mg/l
- Aquatic invertebrate toxicity (Daphnia magna): 33.2 mg/l
- Potential problems related to endangered species: Minimal hazard to
endangered species is expected because of the low toxicity of
paclobutrazol and proposed use (tree injection).
Summary Science Statement
The data base for paclobutrazol (non-food uses) is well developed.
Results of acute inhalation (50% formulation) and eye irritation studies
indicate toxicity category II. The chemical is non-mutagenic and is
rapidly cleared from body tissue (rat and dog studies). Except for sandy
soils, paclobutrazol does not exhibit a tendency to leach. The chemical
does not photodegrade and is not expected to hydrolyze. Hazards to
aquatic and terrestrial wildlife are not anticipated because of low
toxicity and low risk of exposure (tree injection system).
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
- Use classification: General
- Use, formulation, manufacturing process, or geographical restrictions:
Paclobutrazol is not to be injected: (l) into trees that do not
appear healthy, (2) into fruit or nut trees that will be harvested
within one year after application, and (3) into sugar maple or any
other trees that are or could be tapped for sugar.
- Unique label warning statements:
- End-Use Products: Wear protective clothing, rubber gloves, and a
mask or pesticide respirator jointly approved by the Mining
Enforcement and Safety Administration and the National Institute
for Occupational Safety and Health.
5. SUMMARY OF MAJOR DATA GAPS
6. CONTACT PERSON AT EPA
Robert J. Taylor
Product Manager (25), TS-7670
Envlronmental Protection Agency
401 M Street S.W.
Washington, DC 20460
DISCLAIMER: THE INFORMATION PRESENTED IN THIS CHEMICAL INFORMATION FACT
SHEET IS FOR INFORMATIONAL PURPOSES ONLY AND NOT TO BE USED TO FULFILL
DATA REQUIREMENTS FOR PESTICIDE REGISTRATION AND REREGISTRATION.