How should a greenhouse be treated for spider mites in the summer? - briefly
Apply a strong water spray to knock mites off plant surfaces, then treat with a horticultural oil or neem‑based miticide every 5–7 days, removing heavily infested leaves and keeping humidity high to limit reproduction.
How should a greenhouse be treated for spider mites in the summer? - in detail
Effective management of spider mites in a greenhouse during hot months requires an integrated approach that combines monitoring, environmental regulation, cultural practices, biological agents, and, when necessary, targeted chemicals.
Regular scouting is the first line of defense. Inspect leaves every two to three days, focusing on the undersides where mites congregate. Use a 10× hand lens or a portable microscope to count mites per leaf; thresholds of 5–10 mites per leaf tip typically trigger action.
Environmental manipulation reduces mite reproduction. Maintain relative humidity above 60 % by misting or employing humidifiers, because high humidity interferes with egg laying and limits population growth. Keep temperature within the optimal range for the crop (20–25 °C) and avoid excessive heating that accelerates mite life cycles. Provide adequate ventilation to prevent stagnant, dry air.
Cultural tactics limit habitat suitability. Remove heavily infested foliage promptly and destroy it away from the greenhouse. Rotate crops or introduce plant species less attractive to mites to break the infestation cycle. Ensure clean, debris‑free benches and trays, as leaves and organic matter harbor eggs.
Biological control agents offer sustainable suppression. Release predatory mites such as Phytoseiulus persimilis, Neoseiulus californicus, or Amblyseius cucumeris at recommended rates (e.g., 500–1,000 predators per m²). Apply releases weekly until mite numbers decline below economic thresholds. Preserve released predators by avoiding broad‑spectrum insecticides and by providing pollen or yeast supplements as supplemental food.
If mite populations exceed control capacity, selective acaricides can be employed. Choose products with low toxicity to predatory mites, such as sulfur, neem oil, or horticultural oils, and follow label‑specified intervals. Rotate chemicals with different modes of action (e.g., abamectin, spirodiclofen) to delay resistance development. Apply sprays in the early morning or late evening to reduce plant stress.
Sanitation and equipment maintenance support all other measures. Disinfect tools, pots, and conveyance systems with a 70 % ethanol solution or a suitable disinfectant between batches. Quarantine new plant material for at least two weeks and inspect it before introduction.
Implementing these steps in concert—continuous monitoring, humidity elevation, temperature moderation, removal of infested tissue, predatory mite releases, judicious use of selective acaricides, and strict sanitation—provides a robust framework for controlling spider mite outbreaks in greenhouse environments during the summer season.