What's eating my cleistocactus baumannii?

Cleistocactus baumannii, an upright columnar cactus grown outdoors or in bright conservatories, faces aphids on new growth, scale insects on the stem, and spider mites in dry conditions. In garden situations, slugs can damage the base. The main indoor threat is scale. Good airflow and monitoring spines are the first line of defence.

Brown or greyish encrustations on ribs and at spine bases; weakened, yellowing stem sections Scrub with alcohol-dampened brush; apply horticultural oil or systemic neem oil; repeat after 2 weeks

Soft-bodied insects clustering on new growth tips and around flower buds; sticky honeydew Blast off with a firm water spray; apply insecticidal soap or neem oil; introduce ladybirds outdoors

Fine webbing and bronze stippling on the columnar stem, especially in hot, dry spells Increase humidity; spray with neem oil or miticide; ensure good ventilation around the column

Ragged damage to the soft base of columns at soil level, particularly on outdoor or patio plants Use copper tape or grit around the base; apply iron phosphate slug pellets; check at night