What's eating my old lady cactus?

Old Lady Cactus (Mammillaria hahniana) is a globe-shaped houseplant whose dense white wool makes it especially hospitable to mealybugs hiding in the tubercle axils. Scale insects and spider mites are secondary concerns. Root mealybugs can also establish unseen. Inspect the woolly crown regularly — they are easy to miss.

White waxy cottony masses blending into the white wool of the crown and tubercle axils; stunted or absent new growth Dab with 70% isopropyl alcohol on a fine swab; repeat across the entire woolly surface; follow with neem oil spray weekly

Plant wilts and shrinks despite proper watering; white mealy deposits visible on roots when unpotted Remove from pot, shake off soil, treat roots with a neem drench or systemic insecticide, repot in fresh cactus mix

Hard tan or brown bumps on the stem body between the tubercles; localised yellowing Remove with a soft toothbrush dipped in soapy water; apply horticultural oil spray; repeat every 2 weeks