Two-Spotted Spider Mite

Tetranychus urticae — the two-spotted spider mite — is one of the most cosmopolitan and most economically destructive arachnid pests in the world. The species is a 0.5 mm tetranychid mite (eight-legged spider relative, not a true spider) that feeds on the underside of plant leaves, piercing individual epidermal cells with stylet mouthparts and consuming the cell contents. Damaged leaves develop characteristic stippling, then yellowing, then bronzing, then complete defoliation in heavily infested plants. The species' host range is extraordinary: over 1,100 documented host species across most major plant families, including virtually every important horticultural and field crop (tomato, pepper, eggplant, cotton, soybean, corn, strawberry, raspberry, hops, apple, peach, almond, rose, ornamental greenhouse plants). The species is also a major pest of greenhouse crops worldwide and of cannabis cultivation. Damage globally is estimated in the billions of dollars per year. The species' most scientifically-celebrated trait is the genome sequence (Grbić et al., Nature, 2011): T. urticae has an extraordinary expansion of detoxification genes — over 1,000 cytochrome P450, glutathione-S-transferase, ABC transporter, and other xenobiotic-metabolizing genes (typical animals have 50-200). The detox gene expansion explains the species' remarkable ability to evolve resistance to virtually every miticide chemistry ever developed, often within 5-10 years of commercial release. Tetranychus is the textbook organism in chemical ecotoxicology and pesticide-resistance research.