Tiny Bugs in Cactus Roots & Mealybugs on Sempervivum/Sedum

Elaine found tiny black crawling bugs in cactus root soil (like dust), cottony masses on spines, and white deposits on Sempervivum and Sedum leaves.

Two Separate Issues

Likely root mealybugs or fungus gnat larvae in peat-heavy soil.
Fix: Repot in peat-free, porous mix (add perlite/pumice/gravel). Top-dress with ½" gravel. Discard old soil.

Cottony masses = mealybugs.
Treatment: Spray with isopropyl alcohol, pick off with tweezers. Repeat daily 3–5 days. Keep out of sun until rinsed.
Alternatively: Safer's Insecticidal Soap.

Use gritty, inorganic soil; inspect new plants; quarantine.

Cactus: Emergency Pruning for a Frost-Damaged Columnar Cactus; Golden Barrel Cactus Winter Care: Outdoor Dormancy Required; Replanting Found Cactus Piece with Roots: Water, Dry, Add Superthrive; Forgotten Military Cacti: Cold + Wet = Likely Dead; Identifying Small Round Cactus: Beyond Description; Prickly Pear Cutting That Flowered Before Rooting: What to Expect; Can You Root a Yucca Cutting Like a Cactus?; Colorado Potato Beetle: Biological Controls Without Insecticides; Root-Eating Pests in St. Augustine: Likely Grubs — Go Biological; Eating Cactus: Prickly Pear (Nopales) from Garden to Table

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