Root aphids are aphids that feed on roots instead of foliage. On indoor cannabis the main species is the rice root aphid (Rhopalosiphum rufiabdominale), first documented on North American cannabis in 2020. They are olive to dark green, about 1-2 mm long, and often coated with a fine white wax on the roots.
In practice
Root aphids are hard to spot because they live out of sight. Symptoms look like a feeding or watering problem: slow growth, yellowing, wilting between waterings and poor response to feed. Growers find them by tipping a plant out of its pot and inspecting roots and the root ball edge, or by seeing winged adults on yellow sticky traps, often mistaken for fungus gnats. They move between rooms on clones and in reused media. Management combines quarantine, fresh media between runs, and root-zone biologicals such as entomopathogenic fungi and soil predators. Check what is registered for cannabis locally.
Don't confuse with
- Fungus gnat: flies with dangling legs; larvae are clear-bodied maggots, not aphids.
- Root mealybugs: white, cottony, slow-moving and lacking cornicles.
- Root rot: brown, slimy roots with no insects.
Small soft-bodied sap-sucking insects of the family Aphididae that cluster on stems and leaf undersides, excrete sticky honeydew and multiply rapidly by live birth.A coloured card coated in non-drying glue that catches flying insects, used mainly to monitor pest trends: yellow for gnats, whiteflies and aphids, blue for thrips.Small dark flies of the genus Bradysia (family Sciaridae) whose larvae live in wet growing media, feeding on fungi, organic matter and young roots.Soft-bodied sap-sucking insects of the family Pseudococcidae, covered in white waxy filaments, that hide in stem joints and roots and excrete honeydew.Decay of roots by pathogens such as Pythium, Fusarium, Rhizoctonia or Phytophthora, usually triggered by low oxygen, heat and waterlogging around the roots.An entomopathogenic nematode applied as a soil drench whose infective juveniles enter fungus gnat larvae and thrips pupae and kill them with symbiotic bacteria.An insect-killing fungus whose spores germinate on contact, penetrate the cuticle and kill soft-bodied pests such as whiteflies, thrips, aphids and root aphids.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.
