What's eating my melocactus bahiensis?

Melocactus bahiensis, a Brazilian ball cactus with a distinctive woolly cephalium, faces its biggest indoor threat from mealybugs, which readily colonise the cephalium itself. Scale and spider mites attack the body. Damage to the cephalium can prevent flowering. Keep the cephalium dry and inspect it frequently.

White cottony colonies embedded in the cephalium wool and around the body base Dab individual mealybugs with alcohol; avoid wetting the cephalium; apply systemic neem to the soil only

Brown waxy bumps on ribs and spines of the main body below the cephalium Scrub with alcohol-soaked cotton or brush; treat with horticultural oil applied carefully away from cephalium

Fine stippling and discolouration on the green body in warm, dry indoor conditions Wipe the cactus body with a damp cloth; apply miticide spray; increase air circulation around the plant