How to eradicate spider mites in a greenhouse? - briefly
Implement an integrated pest‑management routine: monitor foliage, release predatory mites (e.g., Phytoseiulus persimilis), apply horticultural oil or sulfur sprays when counts increase, and keep humidity moderate while limiting nitrogen fertilization. Seal greenhouse openings and sterilize tools to block re‑introduction.
How to eradicate spider mites in a greenhouse? - in detail
Effective management of spider mites in greenhouse production requires an integrated approach that combines monitoring, cultural practices, biological agents, and, when necessary, selective chemicals.
Regular scouting establishes population thresholds. Inspect the undersides of leaves every 3–5 days using a hand lens or a sticky trap. Record mite counts per leaf area; act when densities exceed 2–3 mites per cm².
Cultural tactics reduce habitat suitability:
- Maintain relative humidity above 60 % to disrupt mite reproduction.
- Keep temperature within 20–25 °C; avoid prolonged periods above 30 °C.
- Provide adequate air circulation with fans to prevent leaf surface stagnation.
- Remove heavily infested plant material promptly.
- Rotate crops and avoid planting host species consecutively.
Mechanical removal supports rapid decline:
- Wash foliage with a strong jet of water, dislodging mites and eggs.
- Apply a fine mist of insecticidal soap (2–5 % fatty acid solution) for 5–10 seconds, ensuring thorough coverage of leaf undersides.
- Use a brush or soft cloth to physically scrape mites from small plants.
Biological control offers sustainable suppression:
- Release predatory mites such as Phytoseiulus persimilis, Neoseiulus californicus, or Amblyseius swirskii at rates of 5–10 predators per square meter.
- Introduce predatory insects like Orius spp. for supplemental predation.
- Preserve refuges (e.g., pollen sources) to sustain predator populations.
Selective chemicals are a last resort, applied only after non‑chemical measures have failed:
- Use miticides with low resistance risk, such as abamectin (0.5 mg a.i./L) or spirodiclofen (25 mg a.i./L), following label rates and pre‑harvest intervals.
- Rotate chemistries with different modes of action to prevent resistance buildup.
- Limit applications to three per season, and monitor for resurgence after each treatment.
Sanitation reinforces all other tactics:
- Clean benches, trays, and tools with a 10 % bleach solution weekly.
- Disinfect propagation media before reuse.
- Dispose of plant debris in sealed containers.
Resistance management requires vigilance:
- Keep records of mite counts, predator releases, and pesticide applications.
- Adjust strategies promptly when populations rebound despite control measures.
By integrating these practices, greenhouse operators can achieve consistent, long‑term suppression of spider mite infestations while minimizing chemical inputs and preserving crop quality.