How to defeat spider mites in a greenhouse? - briefly
Effective management of greenhouse spider mite infestations combines vigilant monitoring, environmental adjustments, and targeted controls; maintain moderate humidity, prune affected foliage, and introduce predatory mites such as Phytoseiulus persimilis. Apply selective miticides only when population thresholds are surpassed, rotating active ingredients to prevent resistance.
How to defeat spider mites in a greenhouse? - in detail
Spider mites thrive in warm, dry greenhouse conditions, feeding on the undersides of leaves and causing stippling, chlorosis, and reduced yield. Early detection relies on regular scouting with a hand lens, focusing on leaf margins and the presence of webbing. A threshold of five mites per leaf warrants intervention.
Cultural tactics reduce population buildup. Maintain relative humidity above 60 % by misting or using humidifiers, which discourages mite development. Avoid excessive nitrogen fertilization; balanced nutrition limits leaf tissue that attracts feeding. Remove heavily infested plant material promptly and rotate crops to interrupt the mite life cycle.
Biological agents provide sustainable control. Predatory mites such as «Phytoseiulus persimilis», «Neoseiulus californicus» and «Amblyseius swirskii» are released at a rate of 10–20 predators per m², targeting all mobile stages of the pest. Ensure adequate leaf surface humidity (≥50 %) for predator establishment. Supplementary releases may be necessary after pesticide applications that harm beneficial arthropods.
Chemical options serve as a last resort. Select acaricides with low residual activity, such as sulfur or neem oil, applying according to label rates and rotating active ingredients to prevent resistance. Contact sprays must cover the leaf underside thoroughly; systemic products are ineffective against spider mites. Observe pre‑harvest intervals and safety regulations.
Integrated pest management combines the above measures. Record mite counts, environmental conditions, and control actions in a logbook to evaluate efficacy. Adjust cultural practices, reinforce biological populations, and apply chemicals only when monitoring exceeds the established threshold. This systematic approach maintains plant health while minimizing chemical inputs.