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in 1996. EXTOXNET no longer updates this information, but it may be useful
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E X T O X N E T
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names for products containing triadimefon include Acizol,
Amiral, Bay MEB 6447, and Bayleton (92.6% triadimefon). The
compound may also be found in formulations with other fungicides
such as captan, carbendazim, folpet, dodine, and propineb .
Triadimefon is a General Use Pesticide (GUP). It is a moderately
toxic compound in toxicity class II that carries the Signal Word
WARNING on its label.
Triadimefon is a systemic fungicide in the triazole family of
chemicals. It is used to control powdery mildews, rusts, and
other fungal pests on cereals, fruits, vegetables, turf, shrubs,
and trees. It is available in wettable powder, emulsifiable
concentrate, granular, and paste forms. All data presented refer
to Bayleton unless otherwise specified.
Formulation: It is
available in wettable powder, emulsifiable concentrate, granular,
and paste forms.
- Acute toxicity: Bayleton (92.6%
triadimefon) has an acute oral LD50 of 300 to 600 mg/kg
in rats, about 1000 mg/kg in mice, and about 500 mg/kg in
rabbits and dogs [6,15]. While these LD50 values indicate
lower acute toxicity than many compounds classed as
moderately toxic, triadimefon is classified this way
because of its potential to cause adverse chronic effects
at low to moderate dose levels. Lower potency
formulations of triadimefon have lower acute toxicities
(higher LD50 values). Acute inhalation toxicity of the
compound is moderate. The 4-hour inhalation LC50 is
greater than 0.48 mg/L in rats and approximately the same
in mice . Acute toxicity through skin exposure is also
fairly low. The LD50 values for the dermal toxicity of
technical triadimefon are greater than 1000 mg/kg in rats
and 2000 mg/kg in rabbits [6,15]. Studies of acute
effects in rats have indicated a potential to induce
neurobehavioral effects . Data regarding eye and skin
irritation are inconclusive .
- Chronic toxicity: A number of 2-year
studies have indicated that there are several toxic
responses to low to moderate doses of the compound.
Long-term studies of triadimefon in several species (rat,
mouse, dog) over a range of doses indicated a reduction
in body weight, changes in red blood cell counts, an
increase in blood cholesterol levels, and increased liver
weights . Increased liver weights may be seen as an
adaptation to toxic stress, rather than a toxic endpoint
related to exposure .
- Reproductive effects: Female rats fed up
to 90 mg/kg/day of Bayleton over three generations showed
a number of adverse effects. No effects were noted in the
fetuses at maternal doses below 2.5 mg/kg/day. At the
middle doses tested (around 15 mg/kg/day) the
second-generation offspring experienced a decrease in
weight gain. At the highest dose, the females experienced
a reduction in body weight and a decrease in fertility
. In another study conducted over two generations,
the female rats showed decreased ovary weight at the 2.5
mg/kg/day dose . At 90 mg/kg/day reductions in litter
size, reduced offspring viability and lower birth weight
were observed in second-generation offspring . This
evidence suggests it is unlikely that triadimefon will
cause reproductive toxicity in humans under normal
- Teratogenic effects: The teratogenic
potential of triadimefon is relatively low . Doses
causing birth defects in rats were high enough to also
produce maternal toxicity. Cleft palates were noted in
the offspring of female rats fed moderate doses of 75
mg/kg/day for an unspecified time period. In a second
study, no teratogenic effects were noted in the offspring
of female rats fed 50 mg/kg/day of Bayleton in the form
of an emulsion. In another teratogenic study in rats, rib
deformities were noted at high maternal doses of 90
mg/kg/day . A study of occupationally-exposed female
workers showed that the highest combined dermal and
inhalation level of exposure for workers was around 60 ug
which corresponds to approximately 0.008 mg/kg/shift for
a 70 kg worker, a value considerably lower than the
lowest dose that caused teratogenic effects in test
animals . Thus, it is unlikely that triadimefon will
cause birth defects in humans under normal circumstanes.
- Mutagenic effects: Six separate studies
indicate that the Bayleton compound is nonmutagenic.
Several other tests were inconclusive . It is unlikely
that the compound poses a significant mutagenic risk.
- Carcinogenic effects: In a 2-year
dietary study with mice, the highest dose tested (600
mg/kg/day) did not produce significant increases in tumor
incidence. Due to high mortality, the reliability of this
data is suspect . Another 2-year dietary study in
mice showed increased liver cell hypertrophy (which may
be related to tumor formation) at doses of greater than
36 mg/kg/day in males and 6 mg/kg/day for females.
Increased liver cell adenoma was detected at all levels,
but carcinoma was not detected at any level in this study
. Based on this evidence, no conclusion can be drawn
about the overall carcinogenicity of triadimefon.
- Organ toxicity: Triadimefon has been
associated with changes in the liver, decreased kidney
weights, and altered urinary bladder structure in
laboratory animals exposed to 18 to 60 mg/kg/day. There
is evidence that acute effects on the central nervous
system may also occur .
- Fate in humans and animals: After oral
administration of a single dose of triadimefon, most of
the compound was eliminated unchanged in the urine and
feces within 2 to 3 days. Some breakdown of a small
amount of the compound occurred in the liver. The
compound has a very short residence time in the blood
stream, about 2 1/2 hours . When applied to the skin
of rats, 40% of the applied amount was excreted in urine
and feces within 8 days. Additional amounts (up to 40%)
were recovered unabsorbed from the skin surface and in
the cage .
- Effects on birds: Triadimefon ranges
from slightly toxic to practically nontoxic to birds. For
instance, the compound has an LD50 value of greater than
4000 mg/kg in mallard ducks . Japanese quail are less
tolerant of the compound (LD50 of 2000 mg/kg) and
canaries are even less tolerant (LD50 >1000 mg/kg)
. Even the most tolerant species exhibited some
compound-related acute toxicity such as diarrhea and
regurgitation within 5 minutes of administration of the
highest doses. At the lowest dose tested (500 mg/kg) no
signs of diarrhea were noted .
- Effects on aquatic organisms: The
compound is slightly toxic to fish, indicating that they
are more susceptible to the presence of the compound than
are birds. Bluegill sunfish are the most susceptible,
followed closely by goldfish, with 96-hour LC50 values of
11 mg/L and 10 to 50 mg/L, respectively . The compound
is only slightly toxic to rainbow trout, with a reported
LC50 of 14 mg/L .
- Effects on other organisms: The compound
is nontoxic to honeybees .
- Breakdown in soil and groundwater:
Triadimefon has low to moderate persistence in soils. In
a sandy loam type of soil, half of the initial amount of
the compound was lost within 18 days. In loamy soil the
half-life was much shorter (about 6 days), which
indicates that breakdown of the compound varies with soil
type . Other reported soil half-lives are 14 to 60
days with an average of 26 days . Triadimefon and its
residues are moderately mobile and may have potential to
leach to groundwater .
- Breakdown in water: In water with a pH
3.0, 6.0, or 9.0, almost 95% of the compound remained
after 28 weeks. The compound is very stable in water and
does not readily undergo hydrolysis .
- Breakdown in vegetation: In plants, a
breaddown product is triadimenol , and translocation
and metabolism may vary according to plant species.
Triadimenol is of comparable toxicity to triadimefon.
- Appearance: Triadimefon consists of
colorless crystals .
- Chemical Name:
- CAS Number: 43121-43-3
- Molecular Weight: 293.76
- Water Solubility: 260 mg/L @ 20 C 
- Solubility in Other Solvents: m.s. in
most organic solvents 
- Melting Point: 82.3 C 
- Vapor Pressure: <0.1 mPa @ 20 C 
- Partition Coefficient: 3.1790 
- Adsorption Coefficient: 300 
- ADI: 0.03 mg/kg 
- MCL: Not Available
- RfD: Not Available
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
8400 Hawthorn Road
P.O. Box 4913
Kansas City, MO 64120
- Phone: 816-242-2429
- Emergency: 816-242-2582
References for the information in this PIP can be found in
Reference List Number 8
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