What should be used to treat a greenhouse for spider mite in spring before planting when it is made of polycarbonate? - briefly
Apply a horticultural oil—such as neem or mineral oil—at the label‑recommended concentration to coat all plant material and interior surfaces, which is safe for polycarbonate panels. After treatment, introduce predatory mites (e.g., Phytoseiulus persimilis) to maintain control before planting.
What should be used to treat a greenhouse for spider mite in spring before planting when it is made of polycarbonate? - in detail
Treating a polycarbonate greenhouse for spider mite before the planting season requires a combination of sanitation, cultural practices, and targeted control agents that will not damage the panels or leave harmful residues.
First, remove all organic debris from the structure. Sweep the floor, discard wilted leaves, and wash benches with a mild detergent solution. Rinse thoroughly and allow surfaces to dry completely. This eliminates overwintering sites and reduces the initial mite population.
Second, adjust environmental conditions to make the environment less favorable for spider mite development. Increase ventilation to lower relative humidity below 60 % and maintain daytime temperatures between 18 °C and 24 °C. Use shade cloths or vent openings to prevent excessive heat, which accelerates mite reproduction.
Third, apply a suitable acaricidal treatment. Options compatible with polycarbonate include:
- Horticultural oil (e.g., neem‑based or mineral oil formulations). Apply at a rate of 1–2 % v/v using a low‑pressure sprayer to coat leaf undersides without creating runoff that could fog the panels.
- Insecticidal soap (potassium salts of fatty acids). Use a concentration of 2–5 % and ensure thorough coverage; the solution dries quickly and does not corrode polycarbonate.
- Biorational miticides such as spinosad or abamectin, applied according to label rates. Both are effective against spider mites and leave minimal residues.
- Biological control agents: release predatory mites (e.g., Phytoseiulus persimilis or Neoseiulus californicus) at a density of 50–100 predators m⁻². Distribute them evenly across the growing benches; they will establish a self‑sustaining population that suppresses spider mite colonies.
When using liquid sprays, adopt the following precautions to protect the polycarbonate panels:
- Employ a fine‑mist nozzle to avoid high‑velocity impact that could crack or scratch the material.
- Avoid oil‑based formulations with solvents such as xylene or toluene, as they can degrade the polymer.
- Conduct applications in the early morning or late afternoon to reduce UV‑induced polymer aging.
Finally, establish a monitoring routine. Place sticky traps at the top of each aisle and inspect weekly. If mite counts exceed 5 mites per leaf, repeat the chosen control measure and consider augmenting predator releases.
By integrating thorough cleaning, environmental management, and the appropriate acaricide or biological agent, a polycarbonate greenhouse can be cleared of spider mites before planting, ensuring a healthy start for the upcoming crop cycle.