What's eating my notch cactus?

Notch Cactus (Obregonia denegrii) is a rare, slow-growing houseplant with broad flat tubercles. Its low, open form makes mealybug infestations relatively visible. Root mealybugs in the soil are a serious threat given the plant's slow recovery rate. Spider mites and scale insects are occasional hazards. This endangered species demands extra vigilance.

White cottony deposits in the grooves between tubercles and at the woolly crown; weakening and discoloration of affected tissue Remove with a fine brush soaked in 70% isopropyl alcohol; treat entire plant with neem oil spray; repeat every 7 days for 3–4 weeks

White powdery specks on roots; very slow or zero growth and unexpected softness at the base Carefully unpot, wash roots, dry in shade, and repot in fresh gritty mix; drench with systemic insecticide if problem persists

Flat, disc-like shells attached to the skin of tubercles; yellow patches where feeding occurs Scrape off gently with a soft tool, then apply diluted neem oil; systemic insecticide for persistent infestations