What's eating my ferocactus schwarzii?

Ferocactus schwarzii is a barrel cactus sharing the same indoor pest profile as other Ferocactus: mealybugs in the woolly areoles and root mealybugs in the soil are the primary threats. Scale insects can establish on the ribs. As a slow-growing species, even a moderate infestation causes disproportionate long-term damage.

White cottony deposits in areoles, especially near the crown; reduced growth rate and softening of the cactus body Treat colonies directly with 70% isopropyl alcohol; follow with weekly neem oil spray for four weeks; keep isolated

Unexplained wilt or very slow decline; white waxy insects and residue on roots and inner pot surface Remove all compost, soak roots in imidacloprid solution, air-dry for 3–5 days, repot in fresh sterile gritty mix

Small, hard, fixed bumps on the rib surfaces; localised yellowing and cosmetic scarring of the slow-growing body Pick off with a toothbrush; apply neem or horticultural oil; treat again after two weeks; monitor monthly