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Bacillus thuringiensis
See also The BioPesticide Manual, 2nd Ed., entry 1:16; 1:17; 1:18; 1:19; 1:20; 1:21
Biological insecticide
Bacterium: Schizomycetes: Eubacteriales
NOMENCLATURE
Bacillus thuringiensis
Chemical Abstracts name Bacillus thuringiensis
Scientific name Bacillus thuringiensis Berliner Other names Bt CAS RN [68038-71-1] (also used for the subspp.), formerly [12673-85-7], [62628-54-0] and [67383-05-5]
subsp. kurstaki
Scientific name Bacillus thuringiensis subsp. kurstaki Var. Serotype: 3a, 3b (Novartis) Strain EG2348, EG2371, EG2424, EG7673 (with morrisoni and kumamotoensis toxins), EG7841 (with aizawai toxin), EG7826 (with aizawai toxin) (all Ecogen); Int. 15-313, SA-11, SA-12; M-200(all Novartis); GC-91 (Novartis, a conjugate of kurstaki and aizawai). Other names Btk Development codes SAN 239 I; SAN 415 I; SAN 420 I (all Sandoz); CGA 237218 (mixture with B.t. aizawai) (Ciba-Geigy)
subsp. aizawai
Scientific name Bacillus thuringiensis subsp. aizawai Var. Serotype: H-7 (Novartis) Strain SA-2 (Novartis) Development codes SAN 401 I (Sandoz); CGA 237218 (mixture with B.t. kurstaki) (Ciba-Geigy)
subsp. tenebrionis
Scientific name Bacillus thuringiensis subsp. tenebrionis Var. Serotype: 8a, 8b (Novartis) Strain SA-10 (Novartis) Other names Bacillus thuringiensis subsp. san diego Development codes SAN 418 I (Novartis)
subsp. israelensis
Scientific name Bacillus thuringiensis subsp. israelensis Var. Serotype: H-14 (Novartis) Strain SA-3 (Novartis); EG 2215 (Ecogen) Development codes SAN 402 I (Novartis)
subsp. japonensis
Scientific name Bacillus thuringiensis subsp. japonensis Strain buibui Other names Btj
PROPERTIES
Bacillus thuringiensis
Composition Bacillus thuringiensis is an aerobic spore-forming gram-positive, rod-shaped bacterium, belonging to the family Bacillaceae. At sporulation, in addition to spores, crystals of protein, the delta-endotoxin, are also formed. Form Suspended solid in a fermentation broth or spray dried concentrate. S.g./density Depends on fermentation materials and procedure. Solubility Insoluble in water and organic solvents. Stability Damaged by u.v. light; dry powders stable up to 40 ºC; useful shelf life of aqueous concentrates 0.5 y (40 ºC), 1.0 y (21-25 ºC), >3 y (2-10 ºC); stable at pH 4 to pH 7 (20 ºC); alkaline hydrolysis: 100% in 1 h at pH 11-12.
subsp. kurstaki
Form Crystals and bacterial spores. Stability Shelf life of formulations is 1-3 y.
subsp. aizawai
Form Crystals and bacterial spores. Stability Shelf life of formulations is 1-3 years.
subsp. tenebrionis
Form Crystals and bacterial spores. Stability Shelf life of formulations is 1-2 years.
subsp. israelensis
Form Crystals and bacterial spores. Stability Formulations are stable for 1-2 y in a cool, dry, dark place.
COMMERCIALISATION
Bacillus thuringiensis
Production By fermentation under well-controlled conditions. History This gram-positive bacterium was detected in 1902 in dying larvae of Bombyx mori Lin. by S. Ishiwata (cited by K. Ishikawa, Pathology of the Silkworm) and was characterised after isolation from larvae of Ephestia kuehniella Zell. by E. Berliner (Z. Angew. Entomol., 1915, 2, 29). First used as a microbial insecticide 'Sporeine' against lepidopterous larvae in 1938 (S. E. Jacobs, Proc. Soc. Appl. Bacteriol., 1950, 13, 83). Developed for the control of these pests by several companies, which currently market products. Manufacturers Abbott; Arbico; Becker Microbial
subsp. kurstaki
History B. thuringiensis subsp. kurstaki strains EG2348, EG2371, EG7841 and EG7826 were constructed at Ecogen Inc. (US patent 5080897) through conjugal mating between B. thuringiensis subsp. kurstaki strains (recipient) and B. thuringiensis subsp. aizawai strains (donor); they produce both CryI and CryII crystal proteins. Strains EG2424 and EG7673 were constructed through a multiple step conjugal mating between subsp. kurstaki strain EG2042 (recipient) and subspp. morrisoni, kumamotoensis and kurstaki strain EG2154 (donors) (see US patent 5024837 and C. Gawron-Burke & T. Johnson in Advances in Potato Pest Biology and Management, G. Zehnder, Ed.); it produces both CryIII and CryI crystal proteins. Patents US 5080897; US 5024837 (both to Ecogen) Manufacturers Arbico; Intrachem Bio; Valent BioSciences
subsp. aizawai
Manufacturers Abbott; Valent BioSciences
subsp. tenebrionis
Manufacturers Abbott; Arbico; Valent BioSciences
subsp. israelensis
Manufacturers Abbott; Valent BioSciences
APPLICATIONS
Bacillus thuringiensis
Mode of action Insecticide with stomach action. Following ingestion, the crystals of endotoxin are solubilised; the epithelial cells of the gut are damaged, insects stop feeding and eventually starve to death.
subsp. kurstaki
Mode of action See above. B. thuringiensis subsp. kurstaki cultures produce spores and CryI and CryII or CryIII protein crystals. Death occurs in 1-4 days. Products made from this isolate generally have field activity of less than 7 days. Uses Used for control of lepidopterous larvae in agriculture, horticulture and forestry. Ecogen strain EG2424 is used for the control of Colorado potato beetle, Leptinotarsa decemlineata. Formulation types OF; SC; WG; WP. Compatibility Compatible with a number of acaricides, insecticides, fungicides, spreaders, stickers and wetters, but not compatible with alkaline products. Selected products: 'Agree' (Certis); 'Bactospeine' (Valent Biosciences); 'Batik' (Serotype 3a-3b) (NPP); 'Baturad' (Cequisa); 'Biobit' (Valent Biosciences); 'Condor' ([EG2348]) (Certis); 'Cordalene' (Agrichem BV, Intrachem Bio Italia); 'Costar' ([H3a, 3b]) (Certis); 'Crymax' ([EG7841]) (Certis); 'Delfin' ([H3a, 3b]) (Certis); 'Design' ([GC-91]) (Certis); 'DiPel' (Valent Biosciences); 'Foray' (forestry) (Valent Biosciences); 'Halt' (Biostadt); 'Javelin' ([H3a, 3b]) (Certis); 'Larvo' (Troy Biosciences); 'Lepinox' ([EG7826]) (Certis); 'Raven' ([EG7673]) (Certis); 'Thuricide' ([H3a, 3b]) (Certis, Valent Biosciences); 'Turex' ([GC-91]) (Certis); 'Vault' ([H3a, 3b]) (Certis); 'Vi-Bt' (Vipesco)
subsp. aizawai
Uses Used for the control of lepidopterous larvae (particularly for control of the diamond-back moth) in agriculture, horticulture and forestry, as well as wax moth control. Selected products: 'Florbac' (Valent Biosciences); 'XenTari' (Valent Biosciences)
subsp. tenebrionis
Uses Used for control of Coleoptera, especially the Colorado potato beetle (Leptinotarsa decemlineata). Selected products: 'Novodor' (Valent Biosciences)
subsp. israelensis
Uses Used for control of mosquito and blackfly larvae. Can be used by aerial application. Formulation types SC; WP. Compatibility Not normally used in mixture. Selected products: 'Acrobe' (BASF); 'Bactimos' (public health) (Valent Biosciences); 'Gnatrol' (Valent Biosciences); 'Skeetal' (Valent Biosciences); 'Teknar' (Valent Biosciences); 'VectoBac' (Valent Biosciences)
subsp. japonensis
Uses For control of soil-inhabiting beetles in turf and ornamentals. Compatibility Not compatible with broad spectrum fungicides such as copper compounds.
OTHER PRODUCTS
Bacillus thuringiensis
'Bacilex' (Shionogi, Bayer CropScience); 'Quark' (Valent Biosciences) Discontinued products: 'Bactospeine WP' * (Koppert); 'Certan' * (Steele & Brodie); 'Collapse' * (NPP); 'Novosol FC' * (Ashlade)
subsp. kurstaki
'Able' (Certis); 'Agrobac' (Tecomag); 'Bactec Bt 32' (Plato); 'Bactosid K' (Sanex); 'Bactucide' (Isagro); 'Biocot' (DuPont); 'Cutlass' ([EG2371]) (Certis); 'Delivery' (Certis); 'Ecotech Bio' ([EG2371]) (Ecogen); 'Ecotech Pro' ([EG2348]) (Ecogen); 'Forwarbit' (Forward); 'Insectobiol' (Samabiol); 'Larvo-BT' (Troy Biosciences); 'Rapax' ([EG2348]) (Intrachem Bio Italia) Discontinued products: 'Bollgard' * ([EG2349]) (Ecogen); 'Foil' * ([EG2424]) (Ecogen); 'Jackpot' * ([EG2424]) (Ecogen, Intrachem); 'Steward' * ([H3a,3b]) (Novartis)
subsp. aizawai
Discontinued products: 'Certan' * (Thermo Trilogy)
subsp. tenebrionis
Discontinued products: 'M-one' * (Mycogen); 'Trident' * (Thermo Trilogy)
subsp. israelensis
'Aquabac' (Becker Microbial); 'Bactis' (Isagro); 'Vectocide' (Sanex)
subsp. japonensis
Discontinued products: 'M-Press' * (Mycogen)
ANALYSIS
Bacillus thuringiensis
Activity of B. thuringiensis is measured in i.u. relative to that of a standard product against Trichoplusia ni, Spodoptera exigua, Leptinotarsa decemlineata, Aedes aegypti or other appropriate susceptible species in standardised bioassays. Assays based on the number of spores are not satisfactory for potency determination.
subsp. kurstaki
The active ingredient of Ecogen's B. thuringiensis subsp. kurstaki strains is measured by a modified sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique described by S. Brussock & T. Currier in Analytical chemistry of Bacillus thuringiensis, Hickle and Fitch, Eds. Insect bioassays can also be used to quantify the potency of formulations.
MAMMALIAN TOXICOLOGY
Bacillus thuringiensis
Extensive studies on B. thuringiensis-containing pesticides demonstrate that isolates are not toxic or pathogenic. No adverse effects observed in body weight gain, clinical effects, or on necropsy. Infectivity/pathogenicity studies show that rodents gradually eliminate B. thuringiensis from the body after oral, inhalation or intravenous application.
Observed toxicity at high doses is attributed to the vegetative growth stage, not to the insecticidal protein or to the spores. Early formulations, produced from B. thuringiensis subsp. thuringiensis contained a toxic b-exotoxin.
See review by US EPA, J. T. McClintock et al., Pestic. Sci., 45, 95 (1995). Some data are given under individual subspp. Toxicity class EPA (formulation) III
subsp. kurstaki
Oral No infectivity or toxicity observed in rats at 4.7 ´ 1011 spores/kg. No adverse effects at doses of 1 ´ 108 up to 7 ´ 1012 cfu per rat. Skin and eye No infectivity or toxicity observed in rats at 3.4 ´ 1011 spores/kg. Inhalation No infectivity or toxicity at 5.4 mg/l (2.6 ´ 107 spores/l). NOEL (2 y) for rats 8.4 g/kg b.w. daily; (13 w) for rats 1.3 ´ 109 spores/kg b.w. daily.
subsp. aizawai
Oral No adverse effects at >1 ´ 108 cfu per rat.
subsp. tenebrionis
Oral No adverse effects at >2 ´ 108 cfu per rat (tech.) or at >5 g WP/kg. Skin and eye No skin effects and no systemic involvement (108-109 cfu).
subsp. israelensis
Oral Acute oral LD50 for rats >2.67 g/kg, 1 ´ 1011 spores/kg; for rabbits >2.00 ´ 109 spores/rabbit. Skin and eye Acute percutaneous LD50 for rats >2000 mg/kg (4.6 ´ 1010 spores/kg), rabbits >6.28 g/kg. Inhalation LC50 8.0 ´ 107 spores/rat. NOEL for rats (3 mo) 4 g/kg b.w. daily.
ECOTOXICOLOGY
Bacillus thuringiensis
Fish LC50 >12 ´ 109 spores/l.
subsp. kurstaki
Birds In 63-day feeding trials, chickens receiving up to 5.1 ´ 107 spores/g diet showed no ill-effects. Fish LC50 (96 h) for water gobie (Pomatoschistus minutus) >400 mg/l (as 'Thuricide HP'). Bees Non-toxic to bees; LD50 (oral) >0.1 mg/bee ('Delfin WG').
subsp. tenebrionis
Fish After 28 d exposure to106 cfu/ml, rainbow trout showed no mortality, no pathogenicity. Bees LD50 >100 mg/bee.
subsp. israelensis
Fish LC50 for rainbow trout >370, bluegill >600 (both in mg/l, as 'VectoBac'). LC50 (96 h) for water feeder guppies (Toecilia retriculata) >156 mg/l (as 'Teknar'). Daphnia LC50 (96 h) >25 mg/l (tech.).
ENVIRONMENTAL FATE
Soil/Environment In clay loam of low nutrient status (pH 7.3, pF2, 25 ºC), insecticidal activity declined rapidly in 20 d due to deterioration of the crystals; at pF3, it declined slowly for 500 d; at higher nutrient status, there was a brief 10-fold increase of inoculum applied to soil. As a natural part of the ecosystem, it decays to complex and non-toxic organic compounds.
subsp. kurstaki
Soil/Environment Bacillus thuringiensis subsp. kurstaki spores have a very short persistence in the environment (DT50 10 h), mainly due to their u.v.-light sensitivity.
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