The mode of action of Verticillium lecanii is entomopathogenic, meaning it infects and kills insect pests through a biological process. It works by:

Contact and Adhesion: Its action primarily relies on contact with the insect pest for infection. The conidia (spores) of the fungus come into contact with the insect’s cuticle (outer covering) through various means, such as direct application or by adhering to the insect’s body through physical contact.

Penetration and Infection: Once in contact with the insect’s cuticle, the conidia of Verticillium lecanii germinate, producing specialized structures called appressoria. These appressoria exert mechanical pressure on the insect’s cuticle, facilitating penetration and entry of the fungal hyphae (thread-like structures) into the insect’s body.
Internal Growth and Multiplication: Once inside the insect, the fungal hyphae grow and multiply rapidly. They spread throughout the insect’s body, consuming and digesting the insect’s tissues for nutrients.

Disruption of Vital Organs: As the fungal hyphae proliferate, they interfere with the insect’s vital organs, such as the digestive and circulatory systems. This disruption causes physiological imbalances and eventually leads to the death of the insect.

Spore Production and Release: As the insect becomes thoroughly colonized by Verticillium lecanii, the fungus starts producing and accumulating new conidia within the insect’s body. These conidia are the infectious spores that will be released to infect other potential hosts.

Death and Spreading: After the insect host dies, the fungus continues to grow and sporulate inside the dead body. When environmental conditions are favorable, the fungal conidia are released from the dead insect, spreading the infection to other susceptible insect pests in the vicinity.