How can spider mite be controlled in a greenhouse? - briefly
Use integrated pest management: monitor mite levels, release predatory mites (e.g., Phytoseiulus persimilis) or lady beetles, and apply horticultural oil or neem‑based miticide when thresholds are reached. Keep humidity low, ensure good ventilation, and clean plant debris regularly to limit favorable conditions.
How can spider mite be controlled in a greenhouse? - in detail
Effective management of spider mite infestations in greenhouse production requires integration of several tactics that target the pest’s biology and the environment in which it thrives.
First, establish a rigorous scouting program. Inspect leaves weekly, focusing on the undersides where mites lay eggs and feed. Use a 10× hand lens to count individuals; thresholds of 3–5 mites per leaf indicate the need for intervention. Record data to identify hot spots and monitor population trends.
Second, modify environmental conditions to disrupt mite reproduction. Maintain relative humidity above 60 % whenever crop requirements allow, as low humidity accelerates development. Reduce temperature peaks to 20–25 °C; temperatures above 30 °C shorten the life cycle and increase population growth.
Third, apply cultural measures that limit colonization. Remove plant debris and fallen leaves, which serve as refuge. Rotate crops with non‑host species for at least one growth cycle. Use reflective mulches or aluminum foil strips to repel mites by altering light patterns.
Fourth, introduce biological control agents. Release predatory mites such as Phytoseiulus persimilis, Neoseiulus californicus or Amblyseius swirskii at rates of 10–20 predators per square meter. Ensure the greenhouse remains pesticide‑free for at least 48 hours before release to protect the biocontrol agents. Supplement with entomopathogenic fungi (e.g., Beauveria bassiana) applied as a foliar spray according to label instructions.
Fifth, employ physical controls when infestations are localized. Apply a fine jet of water (≥30 psi) to dislodge mites from heavily affected foliage. Follow with a mild soap solution (2–3 % non‑ionic surfactant) to reduce re‑infestation. Use horticultural oil (e.g., neem or mineral oil) at 0.5–1 % concentration for contact mortality; avoid application during high temperatures to prevent phytotoxicity.
Sixth, resort to selective chemical miticides only after other methods have failed or when population exceeds economic thresholds. Choose products with distinct modes of action (e.g., abamectin, spirotetramat, bifenazate) and rotate them to delay resistance. Apply at the lowest effective rate, covering both leaf surfaces, and observe pre‑harvest intervals.
Finally, implement resistance‑management practices. Alternate biological and chemical tactics, limit the number of applications of any single active ingredient to three per season, and preserve refuges of untreated plants to sustain predator populations.
By combining vigilant monitoring, environmental adjustment, cultural sanitation, biological agents, targeted physical interventions, and judicious chemical use, greenhouse operators can maintain spider mite populations below damaging levels while minimizing pesticide reliance.