What's eating my old man cactus?

Old Man Cactus (Cephalocereus senilis) is vulnerable to mealybugs hiding inside its dense white hair and to root mealybugs in the soil. Scale and spider mites are secondary threats. The woolly coat makes pest detection tricky — inspect the base and crown monthly. Overwatering leading to root rot is also a major killer.

White cottony masses concealed within the long white hairs; weakened stems and sticky deposits at the base Blow out loose pests with compressed air, then treat with 70% isopropyl alcohol on a cotton swab; drench with diluted neem oil; repeat weekly for a month

White powdery specks on roots; stunted growth and wilting even with adequate water Remove from pot, wash roots thoroughly, allow to dry, then repot in sterile cactus mix; drench with imidacloprid solution if infestation recurs

Fine webbing between spines and hairs; dry, stippled skin surface Rinse carefully (avoiding the hair getting waterlogged), then apply diluted neem oil or a miticide; improve air circulation