How to treat spider mites in a greenhouse? - briefly
Apply a miticide (e.g., neem oil, sulfur spray) and release predatory mites such as Phytoseiulus persimilis while keeping humidity low and ventilation high. Regular scouting and removal of heavily infested foliage prevent re‑infestation.
How to treat spider mites in a greenhouse? - in detail
Effective management of spider mite populations in greenhouse production requires an integrated approach that combines cultural, biological, and chemical tactics. Early detection is essential; regular scouting of leaves for stippling, webbing, and tiny moving specks allows action before damage spreads.
Cultural measures reduce the conditions that favor mite development. Maintain relative humidity above 60 % whenever possible, as low humidity accelerates reproduction. Regulate temperature within the optimal range for crops, avoiding prolonged periods above 30 °C, which increase mite activity. Implement sanitation by removing plant debris, pruning heavily infested foliage, and rotating crops to interrupt life cycles. Use reflective mulches or aluminum foil strips to deter mites by disrupting their visual orientation.
Biological control agents provide sustainable suppression. Introduce predatory insects such as Phytoseiulus persimilis, Neoseiulus californicus, or Amblyseius swirskii; release rates depend on infestation severity, typically 10–20 predators per square meter. Augment with entomopathogenic fungi (e.g., Beauveria bassiana) applied as a foliar spray, ensuring adequate coverage and humidity for fungal infection. Preserve native predator populations by avoiding broad‑spectrum insecticides and providing refuges like banker plants.
Chemical options serve as a last resort and must be employed judiciously to prevent resistance. Select miticides with low toxicity to beneficials, such as spirotetramat, abamectin, or neem oil formulations. Rotate active ingredients according to label recommendations, applying the minimum effective dose and observing pre‑harvest intervals. Conduct resistance monitoring by sampling mites after each treatment and adjusting the program if control declines.
A practical implementation schedule might include:
- Weekly visual inspections and humidity checks.
- Biweekly release of predatory mites when thresholds exceed 5 % leaf area damaged.
- Monthly application of a selective miticide if predator populations are insufficient.
- Immediate sanitation actions whenever webbing is detected.
Record-keeping of scouting results, releases, and sprays enables trend analysis and rapid adaptation of the program. By integrating these measures, greenhouse operators can keep spider mite outbreaks below economic injury levels while preserving crop quality and environmental safety.