What's eating my ric rac cactus?

Ric Rac Cactus (Disocactus anguliger) is an epiphytic jungle cactus most bothered by mealybugs hiding in the wave-like stem notches. Spider mites attack in dry indoor air. Scale insects colonise stems and can be confused with the plant's own texture. Fungus gnats breed if the free-draining mix stays too wet between waterings.

White waxy fluff tucked into the scalloped notches along the flat stems; leaves yellow and soften; honeydew drips below Dab each notch with isopropyl alcohol on a cotton bud; spray thoroughly with neem oil solution; repeat every 7 days

Fine pale speckling or silvering of stem surfaces; fine webbing in heavy infestations; worst in low humidity Increase humidity around the plant; wipe stems with a damp cloth; apply insecticidal soap or neem oil spray

Small tan or brown bumps fixed to stems, easy to overlook against the plant's texture; honeydew and sooty mold follow Scrape off gently with a soft toothbrush; treat stems with neem oil or systemic houseplant insecticide