How can spider mites be eliminated in a greenhouse? - briefly
Apply predatory mites (e.g., Phytoseiulus persimilis) together with horticultural oil or sulfur sprays, maintain low humidity and good ventilation, and, when required, use registered acaricides according to label instructions.
How can spider mites be eliminated in a greenhouse? - in detail
Effective control of spider mites in greenhouse production requires an integrated approach that combines cultural, biological, and chemical measures while maintaining regular monitoring.
Accurate identification is the first step. Adult mites are tiny, reddish‑brown, and move rapidly across leaf surfaces; webs appear as fine silk strands on the undersides of leaves. Early detection prevents population explosions.
Cultural practices that reduce mite development include:
- Maintaining humidity above 60 % during the day, as low humidity favors mite reproduction.
- Regulating temperature between 20 °C and 25 °C to limit rapid life‑cycle progression.
- Providing adequate ventilation to avoid stagnant air pockets where mites thrive.
- Removing heavily infested foliage promptly, then disposing of it away from the greenhouse.
- Rotating crops and avoiding continuous monoculture of highly susceptible species.
Biological agents offer sustainable suppression. Predatory mites such as Phytoseiulus persimilis, Neoseiulus californicus, and Amblyseius swirskii can be released at a rate of 5–10 predators per square meter when mite counts reach 5–10 per leaf. Release should occur in the early morning to enhance predator establishment. Supplemental food (e.g., pollen) supports predator longevity during periods of low prey density.
Chemical options are reserved for severe outbreaks. Selective miticides containing abamectin, bifenazate, or spiromesifen provide rapid knock‑down while sparing most beneficial arthropods. Application rates must follow label instructions; repeat treatments are limited to prevent resistance development. Rotating active ingredients with different modes of action mitigates resistance risk.
Sanitation measures reinforce all other tactics. Disinfecting benches, trays, and tools with a 0.5 % bleach solution reduces the likelihood of mite transfer. Quarantine new plant material for at least two weeks before introduction to the production area.
Monitoring continues throughout the production cycle. Sticky traps placed at canopy height capture adult mites and predators, offering a visual index of population trends. Leaf‑sampling protocols—examining ten leaves from random locations weekly—provide quantitative data for decision‑making.
Implementing these strategies in concert establishes a robust management program that suppresses spider mite populations, preserves plant health, and minimizes reliance on broad‑spectrum chemicals.