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Fenoxycarb

Publication Date: 9/93

TRADE OR OTHER NAMES

Trade names for products containing fenoxycarb include Insegar, Logic, Pictyl, Torus and Varikill. Fenoxycarb is often formulated as a grit or corncob bait.

INTRODUCTION

Fenoxycarb is a carbamate insect growth regulator. It is used as a fire ant bait and for flea, mosquito and cockroach control. Fenoxycarb can also be used to control butterflies and moths (Lepidoptera), scale insects, and sucking insects on olives, vines, cotton and fruit. It is also used to control these pests on stored products.

Fenoxycarb is a General Use Pesticide.

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Fenoxycarb is a slightly toxic compound and carries the signal word CAUTION on its label.

Fenoxycarb blocks the ability of an insect to change into an adult from the juvenile stage (metamorphosis). It also interferes with the molting of larvae. Insects have a rigid external covering called exoskeleton. In order to grow and mature, insects must periodically shed or molt their old exoskeleton and produce a new, larger one.

Fenoxycarb is nearly non-toxic to mammals. The oral LD50 of the compound is greater than 16,800 mg/kg (1) in the rat. The dermal LD50 for fenoxycarb in the rat is greater than 5,000 mg/kg. No deaths occurred at this dose. When 5,000 mg/kg were administered to the animals' skin, rats exhibited labored breathing, curved body position and diarrhea (1). Fenoxycarb was not a skin sensitizer when tested on guinea pigs and has only minimal eye irritation when applied to rabbits. The acute inhalation LC50 of fenoxycarb in rats is greater than 480 mg/m3 showing the slightly toxic nature of this substance by this route of exposure (3).

CHRONIC TOXICITY

Rats fed very low doses of fenoxycarb for a year had no compound related effects at or below the 10 mg/kg/day dose. Dogs fed small amounts of the compound for a month and a half experienced no adverse effects at or below 15.9 mg/kg/day (1). Similar results were noted for the compound in mice (1.4 mg/kg) and in rats (0.8 mg/kg) (3). Very few other studies have been conducted on the chronic, long-term toxicity of the compound. Any adverse effects above these feeding levels were not noted in the literature (3).

Reproductive Effects

No information was found.

Teratogenic Effects

With an unknown species, there were no teratogenic effects observed at doses up to 300 mg/kg/day (1).

Mutagenic Effects

According to the Environmental Protection Agency, fenoxycarb is not mutagenic. No additional information was available (1).

Carcinogenic Effects

No information was found.

Organ Toxicity

Rats that had small amounts of fenoxycarb applied to their skin for twenty-one days had increased liver weights (1).

Fate in Humans and Animals

About ninety percent of a dose of fenoxycarb fed to rats was excreted within 96 hours. No residues were found in the animals organs (1).

ECOLOGICAL EFFECTS

Fenoxycarb is practically non-toxic to birds (1). The compound has LD50s greater than 3,000 mg/kg and 7,000 mg/kg in mallard ducks and bobwhite quail, respectively. The dietary LC50 values for these species exceed 20,000 ppm. Duck and quail reproductive studies generated No-Observable- Effect-Levels (NOEL) of 160 ppm and 400 ppm, respectively.

Fenoxycarb is considered moderately to highly toxic to fish with LC50s ranging from 0.66 ppm for rainbow trout to 1.5 ppm for carp. Fish can accumulate fenoxycarb in their bodies up to 300 times the concentration in the water (1). Fenoxycarb is also considered highly toxic to Daphnia (LC50 = 0.6 ppm). However, under labeled use conditions the highest concentrations which the compound should reach are far below (0.1% to 1.0%) the levels of concern for acute toxicity to fish and invertebrates.

In one study, bluegill sunfish accumulated only twenty times the amount of the compound's concentration in the water. Tissue residues of the pesticide quickly declined after the fish were placed in pesticide-free water (6). Therefore, the EPA has indicated that it is unlikely that the compound would pose a threat to endangered aquatic organisms.

Fenoxycarb has demonstrated effects on the growth and reproduction of Daphnia at extremely low levels during chronic laboratory studies (NOEL = 1.6 ppt). These long-term, constant exposure studies do not however, simulate realistic exposures in the environment where degradation is rapid.

When fenoxycarb was applied at rates ranging from 0.015 to 0.03 lbs/acre to ponds, the compound had no effect on a number of different invertebrates including cladocerans, copepods, ostracods and mayfly nymphs. Specific concentrations in the water were not noted (4).

Fenoxycarb is practically non-toxic to bees in acute studies (Contact LD50 > 100 ug/bee; Oral LD50 = 1,022 ppm, and Foliar LT50 > 24 hours). In a worst case field trial with intentionally contaminated pollen (42.2 ppm) and no alternative food source, a maximum of 10 percent pupae mortality was observed. No effects on worker bees, egg laying or larvae development were observed. Long-term effects were not observed.

ENVIRONMENTAL FATE

Fenoxycarb is readily broken down in soil by the chemical action of water (hydrolysis). Residues in soil were no longer detectable three days after application. The compound also has a low potential for leaching from the soil and has a moderate to strong soil binding tendency (1). These characteristics of fenoxycarb in soil indicate that it is unlikely to contaminate groundwater.

The compound is stable to hydrolysis in acidic water. It breaks downs very rapidly in the presence of sunlight (photodegrades) in water. Half of the initial amount of the compound is broken down by this means within five hours (1). It readily attaches onto organic matter which may limit its persistence in water. Residues in the water could be detected for only two days following an aerial treatment of ponds for the control of mosquitoes (6).

Fenoxycarb is expected to break down relatively quickly in plants (3).

PHYSICAL PROPERTIES AND GUIDELINES

Exposure Guidelines:

No tolerances have been set.

Physical Properties:

CAS #: 79127-80-3
Solubility in water: 6 mg/l
Solubility in solvents: hexane, 0.5/100 g; acetone, chloroform, diethylether, methanol 25 g/100 g
Melting point: 53-54 degrees C
Vapor pressure: 1.3 x 10-8 mmhg

BASIC MANUFACTURER

Ciba-Geigy
Agricultural Division
P.O. Box 18300
Greensboro, NC 27419-8300
Telephone: 919-632-6000
FAX: 919-299-8318

Review by Basic Manufacturer:

Comments solicited: April, 1993
Comments received: May, 1993

REFERENCES

  1. U.S. Environmental Protection Agency (1983-85). Chemical Information Fact Sheet. Office of Pesticides and Toxic Substances, Office of Pesticide Programs (TS-766C).
  2. Meister, Richard T. (ed.) 1992. Farm Chemicals Handbook. Meister Publishing Company, Willoughby, OH.
  3. The Agrochemicals Handbook. 1992. The Royal Society of Chemistry, The University, Nottingham, England.
  4. Miura, T., C.H. Schaefer and R.J. Stewart. 1986. Impact of Carbamate Insect Growth regulators on the Selected Aquatic Organisms; A Preliminary Study. Proceedings Papers of the Annual Conference of the California Mosquito Vector Control Association. Vol 54 36-38.
  5. Miura, T. and R.M. Takahashi. 1987. Impact of Fenoxycarb, a Carbamate Growth Regulator, On Some Aquatic Invertebrates abundant in Mosquito Breeding Habitats. Journal of the American Mosquito Control Association Vol 3: 476-480.
  6. Schaefer, C.H., W.H. Wilder, F.S. Mulligan and E.E. Dupras. 1987. Efficacy of Fenoxycarb Against Mosquitoes (Diptera: Culicidae) and its Persistence in the Laboratory and Field. Journal of Economic Entomology 80(1): 126-130.