How should I treat a greenhouse in autumn after harvest, made of polycarbonate, for spider mite? - briefly
Thoroughly clean and disinfect all surfaces, remove plant debris, and apply a registered miticide (e.g., neem‑oil or sulfur spray) at the recommended rate. Seal gaps, lower humidity, and maintain strong airflow to deter any future spider‑mite outbreaks.
How should I treat a greenhouse in autumn after harvest, made of polycarbonate, for spider mite? - in detail
After the crop is removed, begin by clearing all plant debris, soil, and fallen leaves from the interior. Dispose of the material away from the greenhouse to eliminate sources of spider‑mite eggs and larvae.
Inspect the polycarbonate panels for cracks or gaps. Seal any openings with weather‑proof tape or silicone sealant to prevent entry of warm air that encourages mite development. Reduce ventilation to the minimum required for air exchange; close vents and shade cloths during warm days.
Perform a thorough cleaning of the structure. Wash panels, benches, and support frames with a solution of mild detergent and water, followed by a rinse with a 1 % hydrogen peroxide solution. This eliminates residual organic matter that can harbor mites.
Implement cultural controls:
- Remove all weeds and volunteer plants around the greenhouse perimeter.
- Lower the internal temperature by shading the roof with reflective material or painting the panels with a light‑reflective coating.
- Decrease relative humidity to 50 % or lower by using a dehumidifier or increasing airflow with fans.
Apply biological agents if mites are detected. Release predatory mites (e.g., Phytoseiulus persimilis or Neoseiulus californicus) according to manufacturer rates. Distribute the predators evenly on leaves and stems, repeating applications every 7–10 days until populations decline.
If infestation persists, use a targeted acaricide with low residual activity, such as a neem‑oil spray or a spirotetramat‑based product. Apply according to label directions, covering both leaf surfaces and undersides. Rotate to a different mode of action after each treatment to avoid resistance.
After chemical or biological applications, rinse the greenhouse interior with clean water to remove excess residues. Allow the structure to dry completely before sealing it for winter storage.
Store the greenhouse in a dry, frost‑free environment. Cover the polycarbonate panels with breathable fabric to protect against dust while permitting air circulation. Place sticky traps inside the sealed space to monitor any surviving mites during the dormant period.
Before re‑planting in spring, repeat the cleaning and inspection process, re‑apply biological controls if necessary, and verify that temperature, humidity, and ventilation settings are optimized to discourage mite colonization. This systematic approach minimizes the risk of a post‑harvest spider‑mite outbreak and prepares the greenhouse for a healthy growing season.