What's eating my euphorbia horrida?

Euphorbia horrida (African milk barrel) is a spiny, cactus-like houseplant succulent most at risk from mealybugs sheltering between its deep ribs and spine shields. Scale insects crust onto the ribbed stem. Spider mites can cause bronzing in dry indoor air. Always wear gloves when treating — latex sap is toxic.

Cottony white patches between ribs and under spine shields; heavy infestations cause yellowing of the stem surface and stunted growth Dab each colony with isopropyl alcohol on a fine cotton bud; spray neem oil solution thoroughly; repeat every 10 days; wear protective gloves

Hard brown or tan disc-like bumps cemented to ribs and spine bases; drain sap, causing pale pitting and sticky honeydew Prise off scales with a toothpick; scrub with a soft brush and soapy water; apply horticultural oil; avoid skin contact with broken latex

Pale bronzy stippling on the green epidermis between spines; often worst in winter when indoor heating reduces humidity Increase air humidity slightly; spray insecticidal soap targeting rib surfaces; keep plant away from direct heating sources