How to treat cucumbers in a greenhouse for diseases caused by spider mites? - briefly
Apply a miticide such as abamectin or spinosad according to label rates, ensuring thorough coverage of foliage and allowing repeat applications at 7‑10‑day intervals. Complement chemical control with cultural measures: keep humidity low, remove heavily infested leaves, and introduce predatory mites like Phytoseiulus persimilis.
How to treat cucumbers in a greenhouse for diseases caused by spider mites? - in detail
Effective management of spider‑mite problems on greenhouse cucumbers requires an integrated approach that combines monitoring, cultural adjustments, biological agents, and, when necessary, targeted chemicals.
Regular scouting is the foundation of any control program. Inspect the undersides of leaves every two to three days, using a 10 × 10 cm hand lens. Record the percentage of leaves showing active colonies and the number of webs per plant. When the population exceeds 5 % of leaf area, initiate control measures.
Cultural tactics reduce mite reproduction and spread:
- Maintain relative humidity above 60 % during the day; low humidity accelerates mite development.
- Keep daytime temperatures between 22 °C and 26 °C; temperatures above 30 °C favor rapid population growth.
- Provide adequate air circulation with fans to disrupt web formation.
- Remove heavily infested vines and any plant debris that can shelter mites.
- Rotate crops or use a short‑term fallow period between cucumber cycles to break the life cycle.
Biological control offers rapid suppression without residue concerns:
- Release predatory mites such as Phytoseiulus persimilis or Neoseiulus californicus at a rate of 10–20 predators per square meter.
- Apply the entomopathogenic fungus Beauveria bassiana as a foliar spray according to label recommendations; repeat applications every 7 days during high‑pressure periods.
- Encourage natural enemies by planting nectar‑producing companions (e.g., sweet alyssum) along the greenhouse perimeter.
Chemical options serve as a last resort and must be used with resistance‑management principles:
- Select a miticide with a different mode of action from previous applications; rotate between groups such as abamectin (Glu) and spirodiclofen (C).
- Apply the product as a fine mist to the leaf underside, ensuring coverage of webs and crevices; follow the label dose and pre‑harvest interval.
- Limit the number of applications to three per season to delay resistance development.
Post‑treatment verification includes re‑scouting after 48 hours to confirm population decline. If counts remain above threshold, repeat the most effective measure from the previous step, prioritizing biological agents before re‑applying chemicals.
Document all observations, interventions, and outcomes in a greenhouse log. Continuous data collection allows refinement of thresholds and timing, leading to more predictable control of spider‑mite infestations on cucumber crops.