What's eating my cottontop cactus?

Cottontop Cactus (Echinocactus polycephalus) forms dense clumping heads covered in woolly wool and heavy spines that shelter mealybugs effectively. This is the primary pest to watch for, along with scale insects. The wool at the crown can conceal infestations for a long time — use a magnifying glass and pull back wool gently when inspecting.

Cottony pest deposits blend into the plant's natural wool at the crown, causing unnoticed sap drain and weakening. Carefully part the wool and treat with alcohol swabs. Apply neem oil as a drench and spray; repeat every 7–10 days.

Waxy or shell-like bumps on the rib surfaces beneath the wool canopy; honeydew and sooty mold may follow. Remove manually with a toothpick and alcohol. Spray neem oil or horticultural oil solution thoroughly over all heads; repeat in 2 weeks.

Slow decline and reluctance to push new offsets despite healthy watering; white fuzz on roots at repotting. Unpot, wash and air-dry roots, repot in fresh sterile cactus mix. Drench soil once with systemic insecticide.