What's eating my paper spine cactus?

Paper Spine Cactus (Opuntia articulata) is a segmented cactus grown as a houseplant that is most vulnerable to cochineal scale and mealybugs, which shelter in its areoles. Spider mites can colonise the flat pads in hot, dry air. The brittle, detachable segments mean handling for treatment must be done carefully with gloves.

Powdery white patches on pads that bleed bright red when touched; pads turn yellow and drop in severe infestations. Remove affected pads carefully; scrub remainder with a soft brush and alcohol; spray entire plant with neem oil every 10 days.

Waxy white fuzz around areoles and between segment joints; honeydew and sooty mould. Dab individually with an alcohol swab; spray with insecticidal soap or neem oil; repeat every two weeks.

Pale, dusty stippling on pad surfaces; webbing visible in bad cases; pads look dull and dry. Increase ambient humidity, wipe accessible surfaces, and apply insecticidal soap or neem oil spray weekly until clear.