How should I treat soil for spider mite in a greenhouse in spring before planting? - briefly
Apply solarization or steam sterilization to eradicate existing mites, then incorporate biological controls such as predatory Phytoseiulus persimilis or entomopathogenic nematodes before sowing. Finish with a light, well‑drained organic amendment and keep humidity low to prevent re‑infestation.
How should I treat soil for spider mite in a greenhouse in spring before planting? - in detail
Treat the growing medium before the first crop to minimise spider‑mite outbreaks. Begin with a thorough sanitation routine: remove all plant debris, old mulch, and any cracked pots. Discard or compost material that shows signs of mite activity; do not reuse it.
Conduct a soil‑temperature check. Maintain a range of 18‑22 °C (64‑72 °F) during the seedling phase; lower temperatures suppress mite reproduction, while excessive warmth encourages rapid population growth.
Adjust moisture levels. Keep the substrate evenly moist but not water‑logged; a humid environment (60‑70 % relative humidity) discourages mite dispersal and encourages natural enemies. Use a calibrated irrigation system to avoid dry spots that become refuges for pests.
Incorporate organic amendments that enhance beneficial micro‑fauna. Add a modest dose of well‑composted material, such as vermicompost, to increase microbial diversity. Apply a thin layer (1–2 cm) of diatomaceous earth or horticultural sand on the surface; these abrasives impede mite movement and reduce egg viability.
Introduce biological control agents before planting. Release predatory mites (e.g., Phytoseiulus persimilis, Neoseiulus californicus) at a rate of 10–15 mites m⁻² onto the prepared soil. Ensure the substrate is free of residual pesticides that could harm the released predators.
If chemical intervention is unavoidable, select a miticide with low persistence and minimal impact on beneficial organisms. Apply a soil‑drench of neem‑based product at the label‑recommended concentration, following a flush with clean water after 24 hours to prevent phytotoxicity.
Finally, implement a monitoring schedule. Inspect the top 2 cm of the medium weekly with a 10× hand lens. Record mite counts and adjust humidity, temperature, or predator releases accordingly. Consistent observation allows early detection and rapid response, maintaining a mite‑free environment for the upcoming crop.