Biocontrol of Colorado potato beetle — Which entomopathogenic fungus is widely documented to infect and suppress Leptinotarsa decemlineata in the field?

Introduction / Context:
The Colorado potato beetle (Leptinotarsa decemlineata) is a notorious defoliator of potato and other Solanaceae. Biological control using entomopathogenic fungi offers a sustainable complement to chemical insecticides and helps manage resistance. Recognizing the best-studied fungal agents improves integrated pest management decisions.

Given Data / Assumptions:

• Target pest: Colorado potato beetle (coleopteran).
• Common entomopathogenic fungi: Beauveria bassiana, Metarhizium anisopliae, Verticillium lecanii (Lecanicillium), Nomuraea rileyi (now Metarhizium rileyi).
• Host ranges vary; some fungi specialize in hemipterans or lepidopterans.

Concept / Approach:
Beauveria bassiana is broadly effective against many beetles, including the Colorado potato beetle, with commercial formulations registered in several regions. While Metarhizium anisopliae also targets certain beetles, B. bassiana has the strongest association and literature base for CPB suppression, especially under temperate field conditions.

Step-by-Step Solution:

Verification / Alternative check:
Extension guides and peer-reviewed trials report significant CPB mortality with B. bassiana sprays under conducive humidity and temperature.

Why Other Options Are Wrong:

Common Pitfalls:
Overlooking environmental requirements: high humidity aids infection; UV and heat reduce spore viability, affecting field performance.

Final Answer:
Beauveria bassiana.