Bacillus thuringiensis subsp. kurstaki Manufacturer & Exporter | Larvicides | Microbial Species

Bacillus thuringiensis subsp. kurstaki

Bacillus thuringiensis subsp. kurstaki (Btk) is a gram-positive, spore-forming bacterium naturally found in soils worldwide. It is renowned for its specificity and effectiveness in managing lepidopteran pests, particularly during the larval stage. As a biological insecticide, Btk has become a cornerstone of integrated pest management (IPM) and organic agriculture, combining high efficacy with environmental safety.

Strength

1 x 10⁸ CFU per gram / 1 x 10⁹ CFU per gram / 1 x 10¹⁰ CFU per gram

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Benefits

Compatible with IPM

Integrates well with Integrated Pest Management (IPM) practices.

Environmental Safety

Harmless to beneficial insects like bees and other pollinators.

Residue-free

Leaves no harmful residues on plants or in the environment after application.

Targeted Pest Control

Targets and effectively controls the larvae of lepidopteran pests such as caterpillars.

Scientific References

Scientific References and Resources

Health Canada, PMRA. Btk – Bacillus thuringiensis subspecies kurstaki Fact Sheet.
United States Environmental Protection Agency (EPA).
Biopesticide Fact Sheet: Bacillus thuringiensis.
EPA Biopesticide Registration Information
Bacillus thuringiensis: A story of a successful bioinsecticide.
Insect Biochemistry and Molecular Biology, 41(7), 423–431.DOI:10.1016/j.ibmb.2011.02.006
Bacillus thuringiensis: a century of research, development and commercial applications.
Plant Biotechnology Journal, 9(3), 283–300.DOI:10.1111/j.1467-7652.2011.00595.x
WHO/IPCS (1999).Bacillus thuringiensis. Environmental Health Criteria World Health Organization.
Glare, T. R., & O’Callaghan, M. (2000).Bacillus thuringiensis: Biology, Ecology and Safety

Mode of Action

Btk’s insecticidal action is based on the production of parasporal crystalline inclusions containing Cry and Cyt protein toxins during sporulation. Upon ingestion by susceptible larvae (primarily of the order Lepidoptera), the following steps occur:

Solubilization: The alkaline pH of the insect midgut (>9.0) solubilizes the crystal proteins.
Activation: Solubilized protoxins are proteolytically cleaved by midgut proteases into active toxins.
Receptor Binding: Activated toxins bind to specific receptors (cadherins, aminopeptidases, and alkaline phosphatases) on midgut epithelial cells.
Pore Formation: Binding induces membrane insertion and pore formation, disrupting ionic homeostasis.
Cell Lysis and Septicemia: Midgut cells lyse, leading to paralysis of the digestive tract. The insect ceases feeding and dies within 24–72 hours, typically from starvation or septicemia caused by opportunistic microbes.

This highly selective mode of action ensures that Btk does not affect non-target organisms, including pollinators, predators, or mammals.

Additional Info

Target Pests

Btk is effective against a wide array of lepidopteran pests, such as:

Agricultural: Cabbage looper (Trichoplusia ni), diamondback moth (Plutella xylostella), corn earworm (Helicoverpa zea), armyworms (Spodoptera spp.)
Forestry: Gypsy moth (Lymantria dispar), spruce budworm (Choristoneura fumiferana), tent caterpillar (Malacosoma spp.)
Horticultural: Fruit borers, leafrollers, and cutworms
Recommended Crops: Broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, kale, and turnips

Safety and Environmental Profile

Human Safety: Non-pathogenic to humans. Btk spores and Cry proteins are inactivated in acidic stomachs. Evaluated for dermal, ocular, and inhalation toxicity with no adverse effects. No reports of endocrine disruption.

Non-Target Safety: No toxicity observed in honeybees, fish, birds, amphibians, or mammals. Btk acts only on larval Lepidoptera due to receptor-specific activation.

Environmental Fate: Btk spores and toxins degrade under UV exposure and microbial action. Does not bioaccumulate or leach beyond 25 cm in soil.

Regulatory and Organic Status

Certifications: OMRI-listed; approved for use in EU organic systems.
Regulatory Status: Classified as a "Restricted Product" in Canada—requires certified applicator and permit. Similar restricted use classifications apply in EU and U.S. under EPA regulations.
Residue Tolerance: Exempt from MRLs (maximum residue limits) due to minimal risk.

Dosage & Application

Wettable Powder: 18000 IU per milligram

Foliar Application:

Dose: 3-5 g/L water
1 Acre dose: 600 g - 1 Kg
1 Ha dose: 1.5 - 2.5 Kg
Apply at the early incidence of caterpillar pests. Spray twice at weekly intervals after the first application.

Foliar Application Method

Foliar application should be performed at the early onset of pest incidence. Follow up with 1-2 additional sprays at weekly intervals.
Mix Bacillus Thuringiensis Subsp. Kurstaki at recommended doses in sufficient water and spray on foliage, fruit, or plants.

Note: Do not store Bacillus Thuringiensis Subsp. Kurstaki solution for more than 24 hours after mixing with water.

FAQ

What makes Btk more suitable than chemical insecticides for caterpillar control?

Btk offers selective toxicity, posing no threat to non-target fauna or humans. It supports beneficial insects and microbial soil health and avoids resistance buildup when rotated effectively.

Does Btk affect butterflies?

Only the larval (caterpillar) stage is susceptible. To protect non-target caterpillars, timing and location of applications should be carefully managed.

Can Btk be used in organic farming?

Yes. Btk is certified organic, OMRI-listed, and widely used by organic producers globally.

How fast does Btk work?

Larvae stop feeding within hours, and mortality occurs in 2–5 days depending on species and exposure.

Is it safe to harvest crops after Btk application?

Absolutely. Since Btk is non-toxic to humans and degrades rapidly, there is no pre-harvest interval required.