What's eating my spiny club cactus?

Cereus hildmannianus is a large, robust column cactus that is relatively pest-resistant, but mealybugs and scale insects can colonise the areoles and ribs of tall specimens where they go unnoticed. Spider mites occur in dry indoor air. Its size means infestations can become advanced before they are spotted; inspect ribs carefully.

Brown or tan oval bumps fixed to ribs or areoles; honeydew drips and causes dark sooty mould below Scrape off with a stiff brush, wipe down with alcohol, apply horticultural oil; repeat after two weeks

White fluffy deposits in areoles or at the base of the column; growth tip may wither Dab colonies with alcohol-soaked cotton; spray whole plant with diluted neem oil; isolate from other cacti

Fine yellowish stippling on green stem skin; silvery sheen in dry heated indoor conditions Wipe stem with a damp cloth; mist lightly to raise humidity; apply insecticidal soap or neem oil spray