Bacillus thuringiensis: Biological Weapon against Bugs"

 

Bacillus thuringiensis:  Biological Weapon against Bugs"

Fig:Bacillus thuringiensis

Bacillus thuringiensis (Bt) is a gram positive spore forming bacteria found on 96% of mulberry trees, acting as a potent bio-insecticide against caterpillar pests like webworms, caterpillars, mosquito larvae, black flies, beetle larva and fungus gnats. Bacillus thuringiensis contain Beta exotoxin crystalline protein (Bt) which has revolutionized the world of Organic agriculture and pest management. Bt acts as "biological weapon" that targets specific pests while keeping your garden's beneficial insects like bees and ladybugs completely safe.

 

"Stomach Ache" (Mode of Action)

Beta exotoxin doesn’t kill directly on contact; it must be ingested to work.

Action of Beta exotoxin in pest killing

 

Ingestion: A hungry larva like a caterpillar) eat a leaf treated with Bt spores and crystalline proteins.

1.      Activation: Once the beta exotoxin enters the insect's gut, the alkaline (high pH) environment dissolves the protein crystals and transform them into active toxins.

2.      Mode of action inside body ": It acts as an ATP analog, inhibiting DNA-dependent RNA polymerase by competing for ATP binding sites. This disrupts the synthesis of RNA, leading to death or severe developmental abnormalities.

3.      Pore Formation & Starvation: The toxins enters in the gut wall, causing the insect to stop feeding within 30 minutes. The pest eventually dies from starvation or infection within 1–5 days.

Fig: Bugs killing cycle

Choose your Specialist Bt. Strains

Different subspecies (strains) of Bt produce distinct Cry toxins, making them effective against specific insect groups: 

1.Bt subsp. kurstaki (Btk): Kills lepidopteran larvae (caterpillars of moths and butterflies).

2.Bt subsp. israelensis (Bti): Used for controlling and killing of dipteran larvae (mosquitoes, black flies, and fungus gnats)

3.Bt subsp. aizawai (Bta): Effective against lepidopteran larvae, often used when resistance to Btk is observed.

4. Bt subsp. tenebrionis / japonensis:  It targets coleopteran insects (beetle larvae). 

Why Farmers should use  Bt. pesticides

1.Organic Certified: Approved for use in organic farming because of containing  naturally occurring substance.

2.Eco friendly: Targets specific pests and protects beneficial insects like bees, butterflies, and ladybugs, which are essential for pollination .

 3.Soil Health management: Preserves soil from synthetic chemicals helping to maintain soil

fertility and structure.

4. Control Pollution: Easily biodegradable, help to control air,water pollution, hence enhance aquatic lives.Improved Safety for Workers: : It is non-toxic to humans,

6. Increased Crop Yields: By protecting crops from pests, insecticides prevent destruction, leading to higher, more consistent yields

>Tips for Better Results

·         Target Young Larvae: Apply Bt when target insect larvae are young as it work best on young and actively feeding larvae (less than 5 mm long).

·         Full coverage spray : Spraying of Bt. shall be done properly to cover all plant surfaces, including the undersides of leaves, so the pests will ingest the toxin when they feed.

·         Time of Spray: Spray  Bt in the late afternoon or on cloudy days. Strong sunlight and high temperatures break down Bt spores quickly, reducing its effectiveness.

Avoid Washing Off: Reapply Bt if heavy rain occurs within 48 hours of application.