What should be done with spider mite in a greenhouse in autumn? - briefly
Reduce temperature and humidity, prune and discard heavily infested foliage, and apply a targeted acaricide or release predatory mites. Maintain strict sanitation and weekly monitoring until the greenhouse is winterized.
What should be done with spider mite in a greenhouse in autumn? - in detail
Effective management of spider mites in a greenhouse during the fall requires an integrated approach that combines monitoring, environmental adjustments, cultural practices, biological agents, and, when necessary, targeted chemical treatments.
Regular scouting is the first line of defense. Inspect leaves weekly, focusing on the undersides where mites congregate. Use a hand lens or a sticky trap to quantify populations; thresholds of 5–10 mites per leaf tip typically trigger intervention.
Environmental manipulation reduces mite reproduction. Lower daytime temperatures to 18–20 °C and maintain relative humidity above 60 %. Increase ventilation to disperse heat and limit leaf surface drying, which favors mite development.
Cultural tactics disrupt the pest’s life cycle. Remove plant debris and weeds that can harbor mites. Prune heavily infested foliage and discard it away from the growing area. Rotate crops and avoid planting susceptible species consecutively.
Biological control provides sustainable suppression. Release predatory mites such as Phytoseiulus persimilis or Neoseiulus californicus at rates of 1 predator per 5–10 spider mites. Ensure adequate humidity and avoid broad‑spectrum insecticides that would kill the released agents.
When mite numbers exceed economic thresholds despite the above measures, apply selective acaricides. Choose products with low toxicity to predatory mites, such as neem oil, abamectin, or spirodiclofen, and follow label‑specified rotation intervals to prevent resistance. Apply at the recommended concentration, covering both leaf surfaces.
Sanitation supports all other tactics. Clean tools, benches, and pots with a mild disinfectant between batches. Seal cracks and gaps to prevent external mite ingress.
Maintain records of scouting results, environmental conditions, and control actions. Data trends help refine thresholds and timing for future interventions.