The hemp russet mite (Aculops cannabicola) is an eriophyid mite about 0.2 mm long, carrot-shaped, with only four legs near the head. It feeds only on cannabis and hops relatives, which makes it a hemp and cannabis specialist. It is invisible without strong magnification.
In practice
Damage usually starts low and works up. Leaf edges curl upward, surfaces turn dull, bronze or russet, and petioles can become brittle. In flower the mites crowd into buds and onto trichome stalks, leaving heads that look matted or greasy. By the time a grower notices, populations can number in the thousands per leaf. Confirm with a 40x or stronger scope; the mites look like moving beige dust. Most infestations arrive on clones, so quarantine and inspection of incoming material matter more than any spray. Clean mother stock is the long-term fix. Check what is registered for cannabis locally before treating.
Don't confuse with
- Broad mite: distorts new growth from the top; russet mites start lower and bronze leaves.
- Two-spotted spider mite: visible with a 10x loupe, makes stippling and webbing.
- Rust fungi or nutrient bronzing: no mites under the scope.
Hemp is cannabis grown for fibre, seed or other uses and, in many laws, defined as Cannabis sativa with no more than 0.3% THC by dry weight.The stalk that attaches a leaf to the stem at a node; in cannabis it carries all the leaflets of a palmate leaf.Tetranychus urticae, the commonest cannabis mite indoors: a 0.5 mm sap-feeder that stipples leaves pale and spins webbing, breeding fastest in hot, dry rooms.A hair-like outgrowth of the plant's skin; in cannabis the glandular types make and store the resin holding cannabinoids and terpenes.A mother plant is a female kept permanently in vegetative growth to supply cuttings, so a selected genotype can be propagated as clones indefinitely.Polyphagotarsonemus latus, a microscopic tarsonemid mite whose toxic feeding twists, glazes and stunts new growth; often mistaken for calcium deficiency or heat stress.A small handheld magnifier, typically 30-60x for cannabis use, used to inspect trichome heads and spot pests and male flowers.Holding incoming plants, clones or seeds apart from the main grow, under observation and sometimes treatment, until they are shown to be free of pests and disease.Systematic, regular inspection of plants, traps and roots to detect pests and disease early, identify them correctly and record numbers for decisions.A heated vessel that vaporises elemental sulfur to suppress powdery mildew and mites in veg rooms; it carries fire, gas and timing risks and is never used in flower.
