Mealybugs are scale insects of the family Pseudococcidae, about 2-4 mm long, whose oval bodies are coated in white, mealy wax. They feed on sap through a stylet and excrete honeydew. Foliar species such as the citrus mealybug (Planococcus citri) cluster in leaf axils and stem joints; root mealybugs (Rhizoecus species) live in the root ball.
In practice
Mealybugs are an uncommon cannabis pest and nearly always come in on houseplants or clones from a mixed collection. Look for cottony tufts in branch crotches, egg sacs, honeydew and sooty mould. Root mealybugs show as white waxy patches on the root ball and the inside of the pot. The wax repels water-based sprays, so contact products struggle. Biological control in greenhouses uses the mealybug destroyer beetle (Cryptolaemus montrouzieri) and parasitic wasps. Quarantine incoming plants and keep ornamentals out of the grow. Check what is registered for cannabis locally.
Don't confuse with
- Aphids: no wax coat, faster breeding, cornicles on the rear.
- Powdery mildew: white patches on leaf surfaces that wipe off and have no insects.
- Scale insects: fixed under a hard or waxy shell, not mobile.
Foliar feeding is spraying a dilute nutrient solution onto leaves for quick uptake through the leaf surface; it suits micronutrient fixes but cannot replace root feeding.Using living natural enemies, such as predators, parasitoids, nematodes and microbes, to suppress pests and diseases instead of, or before, chemical sprays.Predatory beetles of the family Coccinellidae, such as Hippodamia convergens, whose adults and larvae eat aphids and other soft-bodied pests.Tiny parasitic wasps of the genus Aphidius that lay eggs inside aphids; the larva kills the host from inside, leaving a swollen tan mummy.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 fungal disease, on cannabis caused mainly by Golovinomyces ambrosiae, that grows as white powdery patches on leaves and buds and thrives in moderate humidity.The protective outer layer of a seed; in cannabis it is fused to the fruit wall and forms the hard shell that cracks open at germination.Sap-sucking insects of the superfamily Coccoidea that settle on stems and leaves under a protective waxy or hard cover; rare on cannabis and usually introduced on other plants.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.Aphids that colonise roots and the crown below the medium surface, on cannabis chiefly the rice root aphid (Rhopalosiphum rufiabdominale), causing slow, unexplained decline.
