How to treat a greenhouse and soil against spider mites? - briefly
Apply horticultural oil or a neem‑based miticide to foliage and a soil drench to target larvae, and introduce predatory mites for biological control. Keep humidity low and clean the greenhouse regularly to suppress reinfestation.
How to treat a greenhouse and soil against spider mites? - in detail
Effective control of spider mites in a greenhouse requires an integrated approach that combines cultural, biological, and chemical measures while maintaining soil health.
First, reduce environmental conditions that favor mite proliferation. Keep temperature between 20 °C and 25 °C and humidity above 60 % whenever possible; low humidity accelerates mite reproduction. Ensure proper ventilation to prevent stagnant air pockets. Remove plant debris and weeds that can harbor pest populations.
Second, implement cultural sanitation. Inspect new plant material before introduction and quarantine any suspect specimens for at least two weeks. Prune heavily infested foliage and dispose of it in sealed bags. Rotate crops annually to interrupt the life cycle of the mite.
Third, introduce natural enemies. Predatory mites such as Phytoseiulus persimilis, Neoseiulus californicus, and Amblyseius swirskii are effective against all life stages. Release rates of 10–20 predators per square meter at the first sign of infestation, followed by weekly augmentations, sustain pressure on the pest. Provide a refuge of pollen or yeast to support predator populations.
Fourth, apply miticidal agents judiciously. Select products with low residual activity to protect beneficial organisms. Recommended options include:
- Neem oil (5 % concentration) – spray until runoff, repeat every 7 days.
- Insecticidal soap (2–3 % fatty acid solution) – apply in early morning or late afternoon, reapply after rain.
- Spinosad (0.5 % suspension) – limited to severe outbreaks, observe pre‑harvest interval.
Rotate active ingredients to prevent resistance. Avoid broad‑spectrum organophosphates, which eliminate predators and disrupt soil microbiota.
Fifth, protect the substrate. Conduct a soil test before planting; maintain organic matter above 3 % to foster a diverse microbial community that competes with mites. Incorporate composted material and beneficial nematodes (Steinernema feltiae) to enhance biological control below ground. Use drip irrigation to keep the root zone moist without creating excess humidity on foliage.
Sixth, monitor continuously. Install sticky traps at canopy level, inspect them weekly, and record mite counts. Use a hand lens (magnification 20×) to examine the undersides of leaves for eggs, larvae, and motile stages. Early detection allows prompt intervention, reducing the need for intensive treatments.
By combining environmental management, sanitation, biological agents, targeted miticides, soil health practices, and diligent scouting, greenhouse operators can suppress spider mite populations while preserving plant vigor and soil integrity.