What does spider mite look like on cucumbers in a greenhouse and how can it be fought? - briefly
Spider mites manifest as minute reddish‑brown dots on the undersides of cucumber leaves, often accompanied by fine silk webs and a stippled, yellow‑ish discoloration of the foliage. Effective control combines frequent scouting, release of predatory mites, and periodic applications of horticultural oil or sulfur sprays while keeping greenhouse humidity low.
What does spider mite look like on cucumbers in a greenhouse and how can it be fought? - in detail
Spider mites on cucumber vines in greenhouse environments appear as tiny, oval‑shaped arthropods, usually 0.2–0.5 mm long. Their bodies are translucent to pale yellow, often showing a faint reddish hue when many individuals congregate. Under magnification, the dorsal surface reveals a pair of long, hair‑like setae that give a fuzzy outline. Mite colonies form on the underside of leaves, where stippled, yellow‑white speckles develop as the insects feed on cell sap. As feeding continues, the speckling coalesces into larger bronzed patches, and leaf tissue may curl, become brittle, or drop prematurely. Fine webbing—silky threads a few micrometres thick—connects the mites and is most noticeable along leaf veins and at leaf margins.
Effective management combines preventive cultural practices, biological agents, and, when necessary, chemical controls.
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Cultural tactics
- Maintain optimal temperature (22–26 °C) and relative humidity (60–70 %). Higher humidity interferes with mite reproduction.
- Ensure adequate air circulation with fans or vent openings to reduce leaf microclimates that favour mite colonisation.
- Inspect new transplants before introduction; quarantine and treat any infested material.
- Remove severely damaged foliage promptly to lower mite reservoirs.
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Biological control
- Release predatory mites such as Phytoseiulus persimilis or Neoseiulus californicus at rates of 10–15 predators per square metre. These agents consume all life stages of spider mites and establish self‑sustaining populations.
- Apply entomopathogenic fungi (e.g., Beauveria bassiana) as a foliar spray; spores penetrate mite cuticles and cause mortality within 48 hours.
- Preserve natural enemy habitats by providing refuges (e.g., clover strips) around the greenhouse perimeter.
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Chemical intervention
- Use acaricides with low residual activity, such as neem oil or abamectin, applying at label‑recommended concentrations and rotating modes of action to delay resistance.
- Conduct systematic monitoring with leaf‑litter traps; treat only when mite counts exceed economic thresholds (typically 5–10 mites per leaf quadrant).
- Follow a strict pre‑harvest interval and observe re‑entry intervals to protect worker safety and crop quality.
Integrated pest management (IPM) relies on regular scouting, accurate identification, and timely implementation of the above measures. By maintaining environmental conditions that deter mite proliferation, augmenting populations of natural enemies, and reserving selective chemicals for outbreak situations, growers can keep spider mite infestations at tolerable levels and preserve cucumber yield and quality.