Mammillaria hahniana · Succulent
Mealybugs: Isolate the plant and treat with a systemic insecticide or dab spots with alcohol-soaked cotton wool.
Root rot: Ensure excellent drainage and keep the plant almost completely dry during winter dormancy.
Scale insects: Scrape off visible scales and apply a horticultural oil spray if infestation persists.
Sunburn: Acclimate plants gradually to brighter light and avoid intense midday sun in early spring.