Mammillaria magnimamma · Succulent
Root rot: Ensure sharp drainage in the potting mix and keep completely dry during winter.
Mealybugs: Isolate the plant and treat with a systemic insecticide or dab spots with alcohol.
Glasshouse red spider mite: Increase humidity slightly and spray with a suitable miticide or horticultural oil.
Glasshouse whitefly: Use yellow sticky traps and apply insecticidal soap or systemic controls if severe.