Treating White Fungus-Like Growth on a Paddle Cactus

A paddle cactus (likely Opuntia) is covered in a white, fungus-like growth. Without a photo, the most common culprits are mealybugs, scale, aphids, or root mealybugs—all of which secrete honeydew that fosters fungal growth. The plant's natural powdery "bloom" (a waxy coating) can also be mistaken for fungus.

If it's pests: isolate the plant immediately. For light infestations, scrape off insects and hose down the plant. For heavy cases, unpot, wash roots, trim dead roots, and repot in fresh, well-draining soil with a systemic insecticide/fungicide. Monitor closely and re-treat at first sign of recurrence.

If the white coating is the natural bloom, no treatment is needed—it's a healthy feature. However, the described "fungus-like growth covering much of the cactus" suggests a pest-driven fungal issue. Overwatering, insufficient light, and poor drainage create ideal conditions for these problems.

Send a photo for definitive identification. In the meantime, improve cultural conditions: ensure rapid drainage, bright light, and dry soil between waterings.