How to combat mites on tomatoes in a greenhouse? - briefly
Use a selective acaricide—such as sulfur, neem oil, or a registered miticide—together with cultural practices like frequent foliage washing and humidity reduction. Augment control with biological agents such as «predatory mites» and monitor populations with sticky traps to keep infestations below damage levels.
How to combat mites on tomatoes in a greenhouse? - in detail
Effective management of mite infestations on greenhouse tomatoes requires an integrated approach that combines monitoring, cultural adjustments, biological agents, and, when necessary, selective chemicals.
Regular scouting is the foundation of control. Inspect leaves at least twice weekly, focusing on the undersides where mites feed. Use a hand lens to detect early signs such as stippling, yellowing, or webbing. Record population levels to determine thresholds for action.
Cultural practices that reduce mite development include:
- Maintaining temperature between 20 °C and 25 °C; temperatures above 30 °C accelerate mite reproduction.
- Controlling relative humidity at 60 %–70 %; low humidity favors spider mites, while excessive humidity promotes fungal diseases.
- Providing adequate air circulation with fans to disrupt mite colonisation.
- Removing plant debris and weeds that can harbour alternate hosts.
Biological control agents offer sustainable suppression. Introduce predatory mites such as Phytoseiulus persimilis, Neoseiulus californicus, or Amblyseius swirskii. Release rates of 10–20 predators per square metre are effective when populations exceed established thresholds. Preserve released agents by avoiding broad‑spectrum insecticides and by supplying supplemental pollen or yeast as food sources.
When mite numbers exceed economic injury levels despite cultural and biological measures, apply selective acaricides. Choose products that target mites while sparing beneficial insects, for example:
- Abamectin at 0.1 mg L⁻¹, applied as a foliar spray, with a re‑treatment interval of 7 days.
- Bifenthrin‑based formulations, limited to two applications per crop cycle to minimise resistance development.
Rotate chemicals with different modes of action and monitor for resistance symptoms, such as reduced efficacy after repeated applications.
Resistant tomato cultivars contribute to long‑term control. Select varieties bred for mite tolerance, and integrate them with the other tactics described.
Sanitation measures close the loop. At the end of each production cycle, remove all plant material, disinfect benches, and sterilise growing media. This eliminates residual mite populations and reduces reinfestation risk for subsequent crops.
Implementing these steps as a coordinated program provides reliable suppression of mite pressure, preserving fruit quality and yield in greenhouse tomato production.