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The information in this profile may be out-of-date.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

Bacillus thuringiensis

Trade and Other Names: Trade names include Acrobe, Bactospeine, Berliner (variety kurstaki), Certan (variety aizawai), Dipel, Javelin, Leptox, Novabac, Teknar (variety israelensis), Thuricide, and Victory. Bacillus thuringiensis is also known at B.t.

Regulatory Status: This microbial insecticide was originally registered in 1961 as a General Use Pesticide (GUP). It is classified as toxicity class III - slightly toxic. Products containing B.t. bear the Signal Word CAUTION because of its potential to irritate eyes and skin.

Chemical Class: bacterium

Introduction: Bacillus thuringiensis (B.t.) is a naturally-occurring soil bacterium that produces poisons which cause disease in insects. B.t. is considered ideal for pest management because of its specificity to pests and because of its lack of toxicity to humans or the natural enemies of many crop pests. There are different strains of B.t., each with specific toxicity to particular types of insects: B.t. aizawai (B.t.a.) is used against wax moth larvae in honeycombs; B.t. israelensis (B.t.i.) is effective against mosquitoes, blackflies and some midges; B.t. kurstaki (B.t.k.) controls various types of lepidopterous insects, including the gypsy moth and cabbage looper. A newer strain, B.t. san diego, is effective against certain beetle species and the boll weevil. To be effective, B.t. must be eaten by insects during their feeding stage of development, when they are larvae. B.t. is ineffective against adult insects. More than 150 insects, mostly lepidopterous larvae, are known to be susceptible in some way to B.t.

B.t. forms asexual reproductive cells, called spores, which enable it to survive in adverse conditions. During the process of spore formation, B.t. also produces unique crystalline bodies. When eaten, the spores and crystals of B.t. act as poisons in the target insects. B.t. is therefore referred to as a stomach poison. B.t. crystals dissolve in the intestine of susceptible insect larvae. They paralyze the cells in the gut, interfering with normal digestion and triggering the insect to stop feeding on host plants. B.t. spores can then invade other insect tissue, multiplying in the insect's blood, until the insect dies. Death can occur within a few hours to a few weeks of B.t. application, depending on the insect species and the amount of B.t. ingested. Typical agricultural formulations include wettable powders, spray concentrates, liquid concentrates, dusts, baits, and time release rings.

Formulation: Typical agricultural formulations include wettable powders, spray concentrates, liquid concentrates, dusts, baits, and time release rings.

Toxicological Effects:

• Acute toxicity: B.t. is practically non-toxic to humans and animals. Humans exposed orally to 1000 mg/day of B.t. showed no effects [146]. A wide range of studies have been conducted on test animals, using several routes of exposure. The highest dose tested was 6.7 x 10^11 spores per animal. The results of these tests suggest that the use of B.t. products causes few, if any, negative effects. B.t. was not acutely toxic in tests conducted on birds, dogs, guinea pigs, mice, rats, and humans. No oral toxicity was found in rats, or mice fed protein crystals from B.t. var. israelensis [147]. The LD50 is greater than 5000 mg/kg for the B.t. product Javelin in rats and greater than 13,000 mg/kg in rats exposed to the product Thuricide [147,148]. Single oral dosages of up to 10,000 mg/kg did not produce toxicity in mice, rats, or dogs [148]. The dermal LD50 for a formulated B.t. product in rabbits is 6280 mg/kg. A single dermal application of 7200 mg/kg of B.t. was not toxic to rabbits [148]. B.t. is an eye irritant; 100 grams of formulated product applied in each eye of test rabbits caused continuous congestion of the iris as well as redness and swelling [149]. Very slight irritation from inhalation was observed in test animals. This may have been caused by the physical rather than the biological properties of the B.t. formulation tested [8]. Mice survived 1 or more 1-hour periods of breathing mist that contained as many as 6.0 x 10^10 spores B.t. per liter [143].
• Chronic toxicity: No complaints were made by 8 men after they were exposed for 7 months to fermentation broth, moist bacterial cakes, waste materials, and final powder created during the commercial production of B.t. [143]. Dietary administration of B.t. for 13 weeks to rats at dosages of 8400 mg/kg/day did not produce toxic effects [143]. Some reversible abnormal redness of the skin was observed when 1 mg/kg/day of formulated B.t. product was put on scratched skin for 21 days. No general, systemic poisoning was observed [8].
• Reproductive effects: There is no indication that B.t. causes reproductive effects [143].
• Teratogenic effects: There is no evidence indicating that formulated B.t. can cause birth defects in mammals [143,148].
• Mutagenic effects: B. thuringiensis appears to have mutagenic potential in plant tissue. Thus, extensive use of B.t. on food plants might be hazardous to these crops [143]. There is no evidence of mutagenicity in mammalian species.
• Carcinogenic effects: Tumor-producing effects were not seen in 2-year chronic studies during which rats were given dietary doses of 8400 mg/kg/day of B.t. formulation [148]. It is unlikely that B.t. is carcinogenic.
• Organ toxicity: There is no evidence of chronic B.t. toxicity in dogs, guinea pigs, rats, humans, or other test animals.

• Fate in humans and animals: B.t. does not persist in the digestive systems of mammals that ingest it [149].

Ecological Effects:

• Effects on birds: B.t. is not toxic to birds [8,150]. The LD50 in bobwhite quail is greater than 10,000 mg/kg. When autopsies were performed on these birds, no pathology was attributed to B.t. Field observations of 74 bird species did not reveal any population changes after aerial spraying of B.t. formulation [148].
• Effects on aquatic organisms: B.t. is practically nontoxic to fish [150]. Rainbow trout and bluegills exposed for 96 hours to B.t. at concentrations of 560 and 1000 mg/L did not show adverse effects. A small marine fish (Anguilla anguilla) was not negatively affected by exposure to 1000 to 2000 times the level of B.t. expected during spray programs. Field observations of populations of brook trout, common white suckers, and smallmouth bass did not reveal adverse effects 1 month after aerial application of B.t. formulation [148]. However, shrimp and mussels may be affected adversely [8].
• Effects on other organisms: Applications of formulated B.t. are not toxic to most beneficial or predator insects [148]. Treatment of honeycombs with B.t. var. aizawai does not have a detrimental effect upon bees, nor on the honey produced [151]. Very high concentrations (108 spores/ ml sucrose syrup) of B.t. var. tenebrionis, which is used against beetles such as the Colorado potato beetle, reduced longevity of honey bee adults but did not cause disease [151]. B.t. applied at rates used for mosquito control may cause the death of some non-target species [8]. Users of B.t. are encouraged to consult local officials or the nearest EPA regional office responsible for protecting endangered species before using B.t. products in counties where susceptible endangered species of Lepidoptera are known to be present [146]. It did not have negative effects on frogs and salamanders [150].

Environmental Fate:

• Breakdown in soil and groundwater: B.t. is a naturally-occurring pathogen that readily breaks down in the environment. Due to its short biological half-life and its specificity, B.t. is less likely than chemical pesticides to cause field resistance in target insects. B.t. is moderately persistent in soil. Its half-life in suitable conditions is about 4 months [152]. B.t. spores are released into the soil from decomposing dead insects after they have been killed by it. B.t. is rapidly inactivated in soils that have a pH below 5.1 [148]. Microbial pesticides such as B.t. are classified as immobile because they do not move, or leach, with groundwater. Because of their rapid biological breakdown and low toxicity, they pose no threat to groundwater.
• Breakdown in water: The EPA has not issued restrictions for the use of B.t. around bodies of water. It can be effective for up to 48 hours in water. Afterwards, it gradually settles out or adheres to suspended organic matter [150].
• Breakdown in vegetation: B.t. is relatively short-lived on foliage because the ultraviolet (UV) light of the sun destroys it very rapidly. Its half-life under normal sunlight conditions is 3.8 hours [153]. It is not poisonous to plants and has not shown any adverse effect upon seed generation or plant vigor [150].

Physical Properties:

• Appearance: The insecticidal action of B.t. is attributed to protein crystals produced by the bacterium. The vegetative cells of B.t. are approximately 1 micron wide and 5 microns long, and are motile [146]. The commercial product contains about 2.5 x 10^11 viable spores per gram. B.t. products lose some of their effectiveness when stored for more than 6 months [8]. B.t. is incompatible with alkaline materials. Formulated products are not compatible with captafol, dinocap, or, under some conditions, leaf (or foliar) nutrients [8].
• Chemical Name: Bacillus thuringiensis [1]
• CAS Number: (B.t. variety kurstaki) 68038-71-1
• Molecular Weight:
• Water Solubility: Not Applicable
• Solubility in Other Solvents: Not Applicable
• Melting Point: Not Applicable
• Vapor Pressure: Not Applicable
• Partition Coefficient: Not Applicable
• Adsorption Coefficient: Not Applicable

Exposure Guidelines:

• ADI: Not Available
• MCL: Not Available
• RfD: Not Available
• PEL: Not Available
• HA: Not Available
• TLV: Not Available

Basic Manufacturer:

Sandoz Agro, Inc., and Abbott Laboratories
1300 E. Touhy Ave.
Des Plaines IL 60018

and

Chem. and Agric. Prod. Div.
1401 Sheridan Rd.
North Chicago, IL 60064

• Phone: 708-699-1616 ; 708-937-2739
• Emergency: 708-699-1616; Not Available
  

References:

References for the information in this PIP can be found in Reference List Number 10

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.