Spider mite appeared on cucumbers in a greenhouse; what should be done? - briefly
Immediately isolate affected plants, wash foliage with a strong jet of water, and treat with an approved miticide such as neem oil or sulfur following label instructions. Continue regular scouting, keep humidity low, and release predatory mites to prevent recurrence.
Spider mite appeared on cucumbers in a greenhouse; what should be done? - in detail
Spider mites can rapidly colonize cucumber crops in protected environments, causing stippling, yellowing, and webbing that reduce marketable yield. Immediate and sustained management requires an integrated approach.
First, confirm the presence of the pest by inspecting the undersides of leaves with a magnifying lens. Look for tiny moving specks, pale stipple patterns, and fine silk threads. A light‑colored leaf surface and dry, warm conditions favor population growth.
Cultural measures
- Reduce temperature to 20‑22 °C where possible; mites thrive above 25 °C.
- Increase relative humidity to 60‑70 % using misting or humidifiers; high moisture interferes with mite reproduction.
- Adjust ventilation to promote air movement, preventing stagnant microclimates.
- Remove heavily infested foliage promptly; discard it away from the greenhouse to eliminate sources of reinfestation.
- Rotate crops with non‑cucurbit species for at least one season to break the mite life cycle.
Biological controls
- Release predatory mites such as Phytoseiulus persimilis or Neoseiulus californicus at a rate of 10–15 predators per square meter.
- Introduce fungal agents (e.g., Beauveria bassiana) as a spray, following label‑specified concentrations.
- Maintain a refuge plant (e.g., bean or pepper) to sustain predator populations between releases.
Chemical options
- Apply acaricides with low residual activity, such as abamectin or spirodiclofen, adhering to the recommended dosage and pre‑harvest interval.
- Alternate products with different modes of action to delay resistance development; consult the resistance management chart for cucumber.
- Use contact sprays early in the morning or late evening to minimize photodegradation and protect beneficial insects.
Monitoring and decision thresholds
- Conduct weekly scouting; record the number of mites per leaf and the percentage of leaf area showing damage.
- Implement treatment when mite density exceeds 5–10 individuals per leaf or when damage surpasses 10 % of foliage.
- Keep detailed logs of interventions, environmental parameters, and pest counts to evaluate efficacy.
By combining environmental adjustments, prompt removal of infected material, augmentative releases of natural enemies, and judicious use of selective acaricides, growers can suppress spider mite outbreaks, preserve cucumber quality, and maintain greenhouse productivity.