Metarhizium is a biological pesticide. To maximize its effectiveness, you must ensure the spores come into direct contact with the pests in a warm, humid environment.
1. Core Principles
- Optimal Timing: Apply during late afternoon, on cloudy days, or in light rain. Metarhizium spores are highly sensitive to UV light and can be killed by direct sunlight.
- Environmental Needs:
- Humidity: Best results occur at >90% relative humidity (essential for spore germination).
- Temperature: Ideal range is 24°C–28°C (75°F–82°F). Effectiveness drops significantly below 15°C (59°F).
- Prohibition: don’t mix with chemical fungicides, as they will kill the live fungus.
2. Application by Formulation
- Oil Suspensions/Emulsions: Dilute with water as per instructions. These are better for low-humidity environments.
- Wettable Powder (WP):
- Pre-mix into a paste with a little water before fully diluting.
- Add a spreader/sticker (e.g., 0.05% vegetable oil or other adjuvants) to help spores stick to the insect’s body.
- Granules: Best for soil-dwelling pests (grubs, cutworms). Apply via soil mixing, hole application, or banding near the root zone.
3. Pest-Specific Strategies
- Locusts/Moths: Focus spray on the underside of leaves where pests congregate.
- Grubs/Soil Pests: Mix with soil or use as a root drench to create a “fungal barrier.”
- Cockroaches: Dust in cracks and crevices or create baits to leverage “horizontal transfer” (secondary infection within the colony).
4. Key Precautions
- Storage: Store in a cool, dry place (4°C–10°C) to maintain shelf life.
- Speed of Action: It is a slow-acting bio-agent. Pests typically die 3–7 days after infection. Use as a preventative measure.
- Safety: Wear a mask and gloves to avoid potential allergic reactions to fungal spores.
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