How to treat a greenhouse for spider mites in spring? - briefly
Begin with a deep sanitation of the greenhouse, discarding infested plant material and cleaning surfaces. Apply a registered miticide—such as neem oil, sulfur, or a horticultural oil—according to label rates, repeat as needed, and keep humidity low to deter further spider‑mite development.
How to treat a greenhouse for spider mites in spring? - in detail
Spider mites proliferate rapidly in greenhouse environments as temperatures rise and humidity drops in early warm months. Prompt identification and a layered management plan are essential to protect crops.
Inspect plants daily for the first signs of infestation: tiny moving dots on leaf undersides, stippled or yellowed foliage, and fine webbing along veins. Use a hand lens or a 10× magnifier to confirm presence. Record affected species, severity, and location to guide treatment decisions.
Implement cultural tactics that reduce mite development:
- Increase ambient humidity to 60‑70 % by misting or using humidifiers; high moisture discourages reproduction.
- Adjust temperature to stay below 80 °F (27 °C) when possible; cooler air slows life cycles.
- Remove heavily infested leaves and destroy them to lower population density.
- Space plants adequately to improve air circulation and reduce micro‑climates favorable to mites.
Introduce biological agents as the primary control measure:
- Release predatory mites such as Phytoseiulus persimilis or Neoseiulus californicus at a rate of 10‑20 predators per m²; repeat releases every 7‑10 days until mite numbers decline.
- Apply entomopathogenic fungi (e.g., Beauveria bassiana) according to label instructions; ensure foliage remains wet for at least 12 hours to allow infection.
- Preserve existing natural enemies by avoiding broad‑spectrum insecticides.
If populations exceed economic thresholds despite cultural and biological actions, employ selective acaricides:
- Use neem‑based oils or horticultural soaps, applying 2‑3 ml L⁻¹ with thorough coverage of leaf surfaces; repeat every 5‑7 days until mites disappear.
- Rotate synthetic products with different modes of action (e.g., spiromesifen, abamectin) to prevent resistance; follow label‑specified pre‑harvest intervals.
- Conduct spot treatments on the most affected plants to limit chemical usage.
Maintain a rigorous monitoring schedule throughout the spring period:
- Examine each crop weekly, noting mite counts per leaf.
- Record environmental parameters (temperature, humidity) to correlate with outbreak peaks.
- Adjust cultural, biological, and chemical interventions based on observed trends.
Preventive measures for subsequent seasons include cleaning greenhouse structures, sanitizing tools, and introducing predatory mites before planting. A systematic, integrated approach ensures effective control of spider mite outbreaks while minimizing chemical inputs and protecting plant health.