How to combat spider mites on tomatoes? - briefly
Apply horticultural oil or insecticidal soap, spraying foliage thoroughly every 5‑7 days and increasing frequency during hot, dry periods; supplement with biological controls like Phytoseiulus persimilis or predatory beetles to keep mite numbers low. Ensure adequate plant spacing, regular watering, and removal of heavily infested leaves to reduce habitat suitability.
How to combat spider mites on tomatoes? - in detail
Spider mites are tiny arachnids that feed on the undersides of tomato leaves, causing stippling, yellowing, and reduced fruit set. Early detection relies on inspecting leaf surfaces with a magnifying lens; the presence of fine webbing confirms an infestation.
Monitoring should be systematic. Examine each plant at least twice weekly during warm, dry periods, when mite populations expand rapidly. Record the number of mites per leaf and the extent of leaf damage to guide treatment thresholds.
Cultural tactics reduce habitat suitability. Remove weeds and plant debris that shelter mites. Space tomato plants 45–60 cm apart to improve air circulation and lower leaf temperature. Water the canopy in the early morning, allowing foliage to dry quickly and discouraging mite reproduction.
Biological agents provide targeted suppression. Release predatory mites such as Phytoseiulus persimilis or Neoseiulus californicus at a rate of 100–200 predators per square meter when mite counts exceed 5 mites per leaf. Maintain humidity above 60 % to enhance predator activity. Apply entomopathogenic fungi (e.g., Beauveria bassiana) according to label instructions; the fungus penetrates mite cuticles and reduces populations within 5–7 days.
Organic sprays offer rapid knock‑down. Mix neem oil (5 ml per liter of water) with a non‑ionic surfactant and apply to both leaf surfaces until runoff. Use insecticidal soap (2 % potassium salts of fatty acids) similarly; repeat every 5 days until mite numbers decline. Avoid applications in direct sunlight to prevent phytotoxicity.
Chemical options are reserved for severe outbreaks. Select a miticide with a short residual activity, such as abamectin (0.5 g L⁻¹) or spirodiclofen (0.2 g L⁻¹), and follow the maximum two‑application limit per season. Rotate products with different modes of action to delay resistance development.
Integrated pest management combines the above measures. Begin with cultural prevention, followed by regular scouting. Introduce predators when thresholds are reached, supplement with organic sprays if needed, and resort to chemicals only as a last step. Maintain records of all interventions to refine future decisions.
Post‑treatment, prune heavily infested foliage and dispose of it away from the garden. Wash tools with a diluted bleach solution (1 % sodium hypochlorite) to eliminate residual mites. Continue monitoring for at least four weeks after the final application to ensure the population remains below economic injury levels.