What's eating my mammillaria mystax?

Mammillaria mystax is susceptible to mealybugs nestling in its woolly areoles and to root mealybugs below the soil. Scale insects and spider mites can occur on stressed plants indoors. The dense central spines make inspection difficult, so check regularly at the growing point and soil surface.

Waxy white wool in the areoles and between tubercles; weakened growth and yellowing if infestation is severe Treat with 70% isopropyl alcohol on a cotton bud; follow up with neem oil or insecticidal soap spray weekly for four weeks

Stunted, wilting plant despite adequate watering; white wax-coated insects on roots discovered at repotting Remove all old compost, treat roots with imidacloprid drench, dry completely before repotting into sterile cactus mix

Brown or tan fixed bumps along the ribs; honeydew and sooty mould on the plant surface Scrape off with a soft toothbrush; apply neem oil or horticultural oil spray; isolate the plant from the collection