What's eating my mammillaria bombycina?

Mammillaria bombycina, like most indoor cacti, is most commonly attacked by mealybugs hiding among its dense spines and wool, and by root mealybugs in the soil. Spider mites and scale insects occasionally infest specimens kept in warm, dry rooms. Overwatering rather than pests is the main killer.

White cottony clusters at the base of spines and in the woolly areoles; plant loses vigour and may yellow Dab individual colonies with a cotton swab dipped in 70% isopropyl alcohol; treat the whole plant with neem oil solution; repeat weekly for a month

Invisible above soil; plant wilts and fails to grow despite correct watering; white waxy fluff visible on roots when unpotted Unpot, wash all soil from roots, soak in a systemic insecticide solution (imidacloprid drench), allow to dry fully, repot in fresh cactus compost

Fine webbing between spines; stippled, dull or russeted skin on the cactus body; worst in hot, dry indoor conditions Raise humidity temporarily; spray with insecticidal soap or neem oil; repeat every 5–7 days for three treatments