How to treat greenhouse cucumbers for spider mites?

How to treat greenhouse cucumbers for spider mites? - briefly

Apply a miticide (e.g., abamectin, spinosad) and release predatory mites such as Phytoseiulus persimilis, while lowering humidity and pruning heavily infested leaves.

How to treat greenhouse cucumbers for spider mites? - in detail

Effective management of spider mite populations on cucumber plants cultivated in protected environments requires an integrated approach that combines monitoring, cultural adjustments, biological agents, and, when necessary, selective chemicals.

Regular scouting is the foundation of any control program. Inspect the undersides of leaves every two to three days, looking for tiny moving specks, stippled foliage, or fine webbing. Record the number of mites per leaf segment; thresholds of 5–10 mites per leaf typically justify intervention in high‑value greenhouse production.

Cultural practices that reduce mite development include:

  • Maintaining relative humidity above 60 % during the day; low humidity accelerates mite reproduction.
  • Regulating temperature to stay within the optimal cucumber range (18–24 °C) while avoiding prolonged periods above 30 °C, which favor rapid mite growth.
  • Providing adequate air circulation with fans to disrupt microclimates that shelter mites.
  • Removing heavily infested leaves promptly to lower the overall population pressure.

Biological control agents offer reliable, residue‑free suppression:

  • Predatory mites such as Phytoseiulus persimilis and Neoseiulus californicus should be released at a rate of 10–15 adults per m² when mite counts exceed the action threshold.
  • Amblyseius swirskii can be employed for early‑season infestations, as it tolerates higher temperatures and also attacks whiteflies.
  • Fungal pathogen Beauveria bassiana formulated as a spray can reduce mite numbers, especially under humid conditions; apply at 1 × 10⁸ conidia L⁻¹ and repeat every 5–7 days until control is achieved.

When biological measures are insufficient, selective acaricides may be used. Choose products with low toxicity to predatory mites and with differing modes of action to prevent resistance. Examples include:

  1. Abamectin (group 6) – apply at the label‑recommended rate, limit to three applications per season.
  2. Spiromesifen (group 23) – effective against immature stages; rotate with other groups.
  3. Bifenthrin (group 3) – reserve for severe outbreaks, observe a 24‑hour re‑entry interval for workers.

After each chemical application, re‑introduce predatory mites to restore biological pressure. Maintain a record of pesticide use, active ingredients, and dates to ensure compliance with resistance‑management guidelines.

Sanitation measures further limit re‑infestation:

  • Disinfect trays, benches, and tools with a 1 % hydrogen peroxide solution between crops.
  • Quarantine new transplants for at least 48 hours, inspecting them for mite presence before introduction to the production area.

Implementing these tactics in a coordinated schedule—monitoring, environmental adjustment, biological releases, targeted chemicals, and strict sanitation—provides robust protection for cucumber yields against spider mite damage in greenhouse settings.