BTK is a gram-positive bacillus isolated from the soil with a bioinsecticidal effect made from selected strains of Bacillus thuringiensis var. Kurstaki for the control of lepidopteran insects, agricultural and forest pests, such as Pieris, Plusia, Heliothis, Plutella, Malacosom, Glena among others.
BTK works by producing proteins (delta endotoxins, known as "toxic crystals") that react with the gut cells of susceptible insects. BTK proteins paralyze the digestive system and the insect stops feeding after a few hours. Occasionally the bacteria can reproduce within the insect.
BTK's mode of action has two aspects that modulate its toxicity:
- Inside the intestine, most insects have an alkaline environment that activates toxins.
- Depending on the species of insect and the nature of its receptors, the toxins of the bacteria may or may not be efficient to infect it.
The greatest effectiveness of BTK occurs during the first and second instar of insects, therefore this is the time for the application of BTK.