What's eating my golden lace cactus?

Golden Lace Cactus (Mammillaria elongata 'Copper King') is a popular columnar houseplant. Mealybugs are the most frequent pest, hiding at the joints of clustered stems. Root mealybugs can go unnoticed for months in the soil. Spider mites attack in dry, heated rooms. Its copper-gold spines can mask mealybug wax — inspect closely each month.

White fluffy deposits at stem joints and growing points; stunted new growth and sticky honeydew residue Dab with isopropyl alcohol swabs; spray plant with diluted neem oil or insecticidal soap; repeat every 7–10 days for four weeks

White powdery coating on roots visible when unpotting; plant declines slowly without obvious above-ground symptoms Unpot, remove old soil, rinse roots, let dry, repot in fresh sterile cactus mix; water with imidacloprid solution if infestation recurs

Fine webbing along spines and dull, grayish patches on the skin surface Rinse plant with water, then apply neem oil or a miticide; increase ambient humidity; repeat treatment in 5–7 days