Spider Mites

Spider mites are the most common and destructive cannabis pest in indoor cultivation, particularly the two-spotted spider mite (Tetranychus urticae). Adult spider mites are 0.5mm long arachnids barely visible to the naked eye, requiring a 10x loupe or higher to identify clearly. They feed by piercing individual leaf cells with sharp mouthparts and sucking out the contents, leaving distinctive damage: small yellow-white "stipple" spots on leaf surfaces (each spot represents one destroyed cell), bronzing or silvering of leaf surfaces in heavy infestations, fine silken webbing covering stems and bud sites, leaf curling and yellowing, and eventually complete leaf death. Reproduction is the terror — adult females lay 100+ eggs in their 30-day lifespan, and eggs hatch in 3-5 days at warm temperatures. A single fertilized female can produce a population of 1+ million descendants in 30 days under optimal conditions. Optimal mite conditions: temperatures 75-85°F (24-29°C), humidity below 50% RH, dusty leaf surfaces, plant stress, dry air conditions. Identification: shake suspect leaves over white paper to see tiny moving dots, inspect leaf undersides with a loupe for adults and white round eggs, look for webbing in canopy crevices. Treatment: predatory mites (Phytoseiulus persimilis, Neoseiulus californicus) provide best long-term biological control without chemical residues; insecticidal soap, neem oil, and rosemary oil work on contact but require 3-5 applications 4 days apart to break the breeding cycle; pyrethrin sprays for severe infestations during vegetative only; aggressive defoliation removing infested leaves; raising humidity above 60% slows reproduction. Spider mites must be eliminated before flowering — once webbing reaches buds, harvest quality is permanently compromised. Quarantine all incoming clones for 14 days under inspection to prevent introduction; this is the #1 source of spider mite infections in clean grow rooms.