What's eating my christmas cactus?

Christmas cactus is most commonly attacked by mealybugs and spider mites indoors. Fungus gnats breed in overwatered soil, and root mealybugs can lurk unseen at the roots. Check stem joints carefully — mealybugs hide in crevices. Catch infestations early with monthly inspections, especially when buds are forming.

White cottony clusters in stem joints and leaf axils; sticky honeydew residue; stunted growth and bud drop. Dab with a cotton swab soaked in 70% isopropyl alcohol; spray with dilute neem oil or insecticidal soap every 7–10 days until clear.

Fine webbing on stems and between segments; stippled or bronzed tissue; segments may shrivel in severe infestations. Raise humidity, rinse the plant under lukewarm water, then apply insecticidal soap or neem oil spray; repeat weekly for 3 weeks.

Tiny black flies around soil; larvae chew fine roots causing wilting and yellowing, especially in soggy compost. Allow the top inch of soil to dry between waterings; use yellow sticky traps for adults; drench soil with Bacillus thuringiensis var. israelensis (Bti) or beneficial nematodes.