Mealybugs, fungus gnats, and root rot: the three problems that actually kill Lithops

Mealybugs hide in the cleft and at the soil line, where the body meets the gravel. The first sign is usually a single white waxy speck, not a colony. Catch it then.

Treatment: a cotton bud dipped in 70% isopropyl alcohol, dabbed directly on every visible bug. Repeat weekly for three weeks to catch the hatch. Avoid broad-spectrum systemic insecticides — they accumulate in the slow-growing body and the residue persists for months.

Adult gnats are an annoyance; the larvae feed on roots and decaying organic matter, including the root cortex of a stressed Lithops. The presence of larvae is almost always a sign your mix is too organic or staying too wet.

Fix the conditions first: top up the top-dressing, reduce watering frequency, and run a fan over the surface. Yellow sticky cards catch the adults. Bti (Bacillus thuringiensis israelensis) drench targets the larvae without harming the plant.

Root rot is not a single disease; it is a fungal opportunist (commonly Fusarium or Pythium) taking advantage of warm-wet soil. The visible body softens, the window darkens to brown or black, and the plant lifts out easily because the roots have liquefied.

A plant that has lost more than half its root mass to rot is usually unrecoverable. For early cases — soft cleft, slight discolouration — unpot, cut back to clean tissue, dust with sulphur, callus dry for two weeks, and reseat in fresh dry mix. Recovery rate is around 40%.