Bacillus thuringiensis (Bt) is a soil-dwelling bacterium widely recognized for its role in biological pest control, but it also provides several benefits to plants through pest management and indirect growth promotion. Below is a concise overview of how plants can benefit from Bacillus thuringiensis:
Biocontrol of Insect Pests:
Bacillus thuringiensis produces insecticidal proteins, known as Cry (crystal) toxins, which are highly specific to certain insect pests, such as caterpillars (Lepidoptera), beetles (Coleoptera), and mosquito larvae (Diptera).
These toxins disrupt the digestive systems of target pests, effectively controlling pests like leaf-eating caterpillars, corn borers, and rootworms, thereby reducing crop damage and protecting plant health.
Unlike chemical pesticides, Bt is safe for non-target organisms, including beneficial insects, pollinators, and humans.
Reduced Plant Damage:
By controlling pest populations, Bacillus thuringiensis minimizes physical damage to leaves, stems, roots, and fruits, allowing plants to maintain healthy photosynthesis, nutrient transport, and growth.
This protection leads to improved crop quality and higher yields.
Indirect Growth Promotion:
By reducing pest-related stress, Bt allows plants to allocate more energy to growth and reproduction rather than defense or repair.
Healthier plants with less pest damage can better absorb nutrients and water, indirectly supporting vigor and productivity.
Environmental and Soil Health Benefits:
Bacillus thuringiensis is a natural biopesticide that reduces the need for synthetic chemical pesticides, promoting a healthier soil ecosystem and reducing chemical residues that could harm plants.
It integrates well into sustainable agriculture and organic farming systems, supporting long-term soil and plant health.
Applications:
Applied as a foliar spray, soil treatment, or seed coating to target pest larvae during their feeding stages.
Used in transgenic crops (e.g., Bt corn, Bt cotton), where plants are genetically modified to express Bt toxins, providing built-in pest resistance.
Formulated as biopesticide products (e.g., Dipel, Thuricide) for use in agriculture, horticulture, and forestry.
Examples:
Bacillus thuringiensis is widely used to protect crops  from pests like caterpillars and borers, leading to increased yields and reduced pesticide costs.
In organic farming, Bt sprays are used to control pests on leafy greens and fruit crops without harming beneficial insects.
Comparison with Bacillus velezensis, Bacillus megaterium, Brevibacillus laterosporus, and Trichoderma harzianum:
Unlike Bacillus velezensis (strong in pathogen control and growth promotion), Bacillus megaterium (noted for nutrient solubilization), Brevibacillus laterosporus (dual pathogen and pest control), and Trichoderma harzianum (focused on fungal pathogen control), Bacillus thuringiensis specializes in insect pest control through its Cry toxins.
Bt has limited direct effects on nutrient availability or fungal pathogen control but excels in protecting plants from insect damage, complementing the benefits of other microbial agents.
Combining Bt with these other microorganisms could provide comprehensive protection against pests, pathogens, and nutrient deficiencies.