What should be sprayed on cucumbers in a greenhouse to control mites? - briefly
Apply a miticide approved for greenhouse cucumbers, such as abamectin, spinosad, or a horticultural oil, following label rates and intervals. Rotate products with different modes of action to prevent resistance.
What should be sprayed on cucumbers in a greenhouse to control mites? - in detail
Effective mite control in greenhouse cucumber production relies on a combination of chemical and biological agents applied according to precise timing and dosage.
Systemic acaricides such as abamectin, milbemectin, or spirodiclofen penetrate plant tissue and eliminate spider mites that feed within leaf pores. These products should be applied at the label‑specified concentration when the first signs of infestation appear, typically when mite populations exceed 5 mites per leaf. Rotate between different mode‑of‑action classes to prevent resistance buildup.
Contact agents provide rapid knock‑down of adult and nymph stages. Recommended options include:
- Horticultural oil (e.g., neem seed oil, mineral oil) at 1–2 % v/v, sprayed until leaves are uniformly coated; effective against all mobile stages but requires thorough coverage.
- Insecticidal soap (potassium salts of fatty acids) at 2–5 % dilution; suitable for early infestations, safe for most beneficial insects when used sparingly.
- Pyrethroid formulations (e.g., bifenthrin, cyfluthrin) at low rates; reserved for severe outbreaks due to higher toxicity to pollinators and natural predators.
Biological control agents complement chemical treatments. Commercial strains of Phytoseiulus persimilis or Neoseiulus californicus are predatory mites that establish populations within the canopy, suppressing pest numbers over several weeks. Release rates of 10–20 predators per m², followed by a light oil spray to improve retention, enhance efficacy.
Cultural measures reduce the need for frequent applications. Maintain relative humidity between 60–70 % and temperature around 22–25 °C to discourage mite reproduction. Remove plant debris, and inspect seedlings before introduction to the greenhouse.
Integrated management protocol:
- Monitor leaf samples weekly with a hand lens; record mite counts per leaf.
- Initiate oil or soap spray when thresholds are reached.
- Apply a systemic acaricide after 5–7 days if oil treatment fails to reduce counts below 2 mites per leaf.
- Introduce predatory mites concurrently with the first spray to establish biological pressure.
- Rotate acaricide class every 10–14 days, respecting pre‑harvest intervals and maximum residue limits.
Safety considerations include wearing protective gloves and goggles during application, calibrating sprayers to achieve droplet size of 150–200 µm, and adhering to re‑entry intervals specified on product labels. Record all treatments in a logbook to track efficacy and resistance trends.