What's eating my quehlianum chin cactus?

Gymnocalycium quehlianum is a slow-growing chin cactus most vulnerable to root rot and root mealybugs indoors. Its shallow root system makes hidden infestations especially damaging. Spider mites may appear in very dry indoor air. Check roots at every repotting and avoid overwatering, which weakens defenses and attracts fungus gnats.

Plant wilts or stays small despite good care; white powdery coating on roots discovered when repotting Remove all old soil, rinse roots, let dry, treat with a systemic insecticide drench or neem soak before repotting

Fine stippling or silvery scarring on the stem surface; fine webbing in severe infestations Raise humidity slightly, wipe plant with a damp cloth, apply insecticidal soap or diluted neem oil

Adult gnats flying around soil; larvae chew fine roots causing wilting and poor vigor Allow soil to dry fully between waterings; use yellow sticky traps; drench with Bacillus thuringiensis israelensis (Bti)