What should be done in a greenhouse in autumn to control spider mites? - briefly
Apply horticultural oil or neem‑based spray early in autumn and inspect plants regularly, removing heavily infested leaves. Keep humidity low and limit nitrogen fertilization to reduce mite reproduction.
What should be done in a greenhouse in autumn to control spider mites? - in detail
Effective autumn management of spider mites in a greenhouse requires an integrated approach that combines monitoring, environmental adjustment, cultural practices, biological agents, and, when necessary, targeted chemicals.
Begin with regular scouting. Inspect leaves every two to three days, focusing on the undersides where mites congregate. Use a hand lens or a sticky trap to quantify population density; thresholds of 5–10 mites per leaf indicate the need for intervention.
Adjust the microclimate to create unfavorable conditions for the pest. Lower relative humidity to 50–60 % by increasing ventilation and using dehumidifiers. Reduce leaf temperature to 20–22 °C, as mites thrive above 25 °C. Maintain adequate airflow to prevent stagnant zones.
Implement sanitation measures. Remove plant debris, fallen leaves, and any infested material. Clean benches, pots, and drip lines with a mild detergent solution, then rinse thoroughly. Disinfect tools with 70 % alcohol or a quaternary ammonium compound before each use.
Adopt cultural tactics that limit mite reproduction. Rotate crops with non‑host species such as lettuce or basil. Provide adequate spacing to improve air movement. Prune heavily infested foliage promptly, and dispose of it away from the production area.
Introduce biological control agents early in the season. Release predatory mites (e.g., Phytoseiulus persimilis, Neoseiulus californicus) at a rate of 1 – 2 predators per leaf, repeating applications every 7–10 days until mite numbers decline. Supplement with entomopathogenic fungi like Beauveria bassiana if humidity permits.
When the population exceeds economic thresholds and biological measures are insufficient, apply selective acaricides. Choose products with low residual activity, such as sulfur or neem oil, and rotate active ingredients to avoid resistance. Follow label rates precisely, and allow a pre‑harvest interval of at least 48 hours.
Maintain detailed records of scouting results, environmental parameters, biological releases, and chemical applications. Analyze trends to refine timing and dosage for subsequent seasons.
By integrating these steps—systematic monitoring, climate control, sanitation, crop rotation, biological releases, and judicious chemical use—autumn greenhouse environments can keep spider mite infestations below damaging levels while preserving plant health and product quality.