What's eating my mandacaru cactus?

Mandacaru Cactus (Cereus jamacaru) is a large columnar cactus that indoors is most vulnerable to mealybugs in the rib grooves and scale insects on the stem. Spider mites can attack in very dry air. The plant's size makes early detection important — check each rib groove when watering and act quickly to prevent spread.

Waxy brown or tan discs on the column; yellow halos around attachment points; sooty mold if honeydew accumulates. Scrub off with a soft brush dipped in dilute isopropyl alcohol. Treat the whole column with neem oil spray; repeat monthly.

Cottony white masses in rib grooves and near the growing tip; sap loss causes shrinking segments. Swab individual colonies with 70% alcohol. Spray neem oil or insecticidal soap thoroughly; isolate from other cacti.

Faint silvery stippling across the green column surface; very fine webbing at the apex in dry conditions. Wipe down with a damp cloth, raise humidity, and apply neem oil spray. Repeat every 5–7 days until symptoms resolve.