What's eating my yucca?

Yucca is a tough houseplant but scale insects are its most persistent enemy, anchoring on the trunk-like stem and beneath the stiff leaf bases. Spider mites attack the leaf surfaces in hot dry conditions. Outdoors, agave weevil can be devastating. Yucca's rigid leaves make physical pest removal harder than with softer-leafed plants.

Tan or brown bumps clustered on stems, at leaf bases, and under leaf margins; yellow patches on leaves; sticky honeydew below plant Scrape off manually; apply horticultural oil or neem oil to all surfaces; repeat every 2 weeks; remove heavily encrusted leaves

Fine stippling and silvery discolouration on leaf surfaces; light webbing; more common in heated, dry indoor air Wipe leaves with a damp cloth; spray with insecticidal soap or diluted neem oil; raise local humidity

White waxy colonies hidden where leaves meet the stem; gradual yellowing and wilting Apply 70% isopropyl alcohol with a cotton swab into each leaf base; spray neem oil; repeat weekly until clear