What's eating my cacti (general care)?

Cacti are tough but not pest-free. Mealybugs are the most common threat, hiding in spine clusters and areoles where they are easy to miss. Scale insects and spider mites also attack, and fungus gnats breed in overwatered, organic-heavy soil. Root mealybugs are a silent killer — suspect them if a cactus declines despite good care.

White cottony fluff between spines and areoles; corky or yellowed patches on the stem; plant stops growing and may shrivel. Apply 70% isopropyl alcohol directly to colonies using a cotton swab; spray with insecticidal soap or neem oil; check roots for root mealybugs and drench with neem if suspected.

Hard brown or grey bumps on the stem surface; yellowing or reddish discolouration around the pest; overall decline. Scrape off with a toothbrush; treat with neem or horticultural oil spray; repeat every 2–3 weeks until no new crawlers are seen.

Rusty, bronze, or silver stippling on the stem surface, often starting at the top; fine webbing visible in dry conditions. Rinse the cactus under running water; apply insecticidal soap or neem oil spray; increase humidity slightly and move away from heat sources.

Larvae in wet soil chew roots and root hairs, stunting growth; adults are a nuisance around the pot. Switch to a very free-draining cactus mix; allow soil to dry completely between waterings; apply Bti drench; use yellow sticky traps.